Abstract: There is disclosed a method for restricting a telephone call in a key telephone or a private branch exchange (PBX). In the method, a user can restrict the telephone call by directly installing a telephone call restricting code when the user intends to restrict a toll call or international call according to the class of extension line. According to the method, a memory table for use in setting a code for allowing or denying a telephone call is designated and the user directly installs a telephone call restriction code on the vacant memory of the designated allowing/denying table and a telephone call is easily restricted according to the installed class designation data. Therefore, the improvement makes it possible to freely restrict an international telephone call as well as a toll call without changing the main program on the system even when the telephone call system of a telephone office switchboard is changed.