PURPOSE: To utilize a video telephone as a crime prevention device.

CONSTITUTION: A picture coder 31 includes a crime preventing device 42 and writes/reads picture data in a picture memory group 33. On the other hand, a multiplexer 34 multiplexes a picture signal and a sound signal coded by the picture coder 31 and a sound coder 32. The crime prevention device 42 is provided with a picture comparator 51 and a judgement device 52 in its inside to compare picture data obtained by photographing an external state for prescribed time as to judge whether they significantly change or not along with the elapse of time.