Korean police can hold an arrestee for up to 10 days before they must bring him a prosecutor. Before suspects are indicted, pretrial detainees, in principles, should be held in detention facilities(jail) under the authorities of the Justice Ministry, not of the investigators. However in almost all cases they are detained in police station cells(lockups) for up to 10, or, in special cases 20 days for the police investigation. To make matters worse in the area where the detention facilities are not sufficient, pretrial detainees and unsentenced detainees are held in police station cells, that is, substitute jail. The police station can be provided with a lockup to intern those who are placed in detention according to the procedures as prescribed by relevant acts, or have received a judgement or have disposition restricting corporal freedom. Thus not only the detained suspects but also those who received penal detention or detention in a workhouse, compulsory appearance etc can be interned in police station cells. In Korea the police custody system has been criticised as a hotbed for infringement on the rights of citizens like coerced confession, violation of right to counsel etc. Recently there are some litigation against police because of execution strip search on persons who was detained in police custody. Strip search has been a hot issue in Korean society, because it humiliate detainees seriously. From the viewpoint of police, keeping the safety and order in custody could be a important thing. But Supreme Court and Constitutional Court of Korea made up a strict principles about the body search. Many issues that have risen in the police station cells have its origin in defects of acts and subordinate statutes on police custody. In this study I tried to handle the problems that cause troubles in police jail and to find ways to solve them from a standpoint of legal system.