In Japan, we can often see many foreign students doing part-time jobs so to foreign students, it should be very common to do part-time jobs. However, some students may not be so clear about the rules and regulations regarding their student visas. Therefore, it is very likely that some foreign students may accidentally break the law without realizing it. 
Many foreign students have about 2-3 months before their visa expires after graduating from a Japanese language school, so some students want to use this time to do part-time jobs. Some students received “Permission to Engage in Activity Other Than That Permitted under the Status of Residence Previously Granted” while they were in school. (Students must get this permission from the Immigration Bureau in order to do part-time jobs. Also must apply while in school.)。With this permission, a student can work up to 28 hours a week. Does that mean that with this permission, a student can continue to work even after graduating from a Japanese language school?
The answer is: NO, you cannot continue to do part-time job after graduation.  Even if your student visa has not yet expired and you have “Permission to Engage in Activity Other Than That Permitted under the Status of Residence Previously Granted”, you will not be able to continue working after you graduate from your Japanese language school.
Many people may wonder why they can’t continue working after graduating from the Japanese language school. This is because a student visa is a visa for students to attend school. After graduation, the effectiveness of this student visa is no longer available. Since the main purpose of a student visa is no longer valid, the permission that you granted to do a part-time job also becomes ineffective. Many language school students may feel that they see many people around them who continue to do part-time jobs after graduating from the Japanese language school. Many of them may not know this is illegal.
Some students graduated and still have more than 6 months before their visa expired. Even though there is still some time left before your visa expired, the Immigration Bureau has the right to cancel your visa if you continue to stay in Japan for more than 3 months after graduation. Therefore please pay special attention and remember to apply for a new visa within 3 months after graduation.
This is a case that has been happening a lot lately. It used to be less stringent, but recently it has become more stringent. Therefore, it is important to remember that you are not allowed to work after graduating from the Japanese language school! If you are worried that there will be no income between graduation and finding a job, which will make your life difficult, it is recommended that you look for a job (job hunting) while you are still in school.
Lastly, to remind those who wish to stay in Japan after graduation, you must remember that you cannot work part-time after graduating from a language school! This is VERY IMPORTANT!