A keyless entry system includes a first communication apparatus and a second communication apparatus. The first communication apparatus includes first transmitter, first receiver, and first two-way communication device. The second communication apparatus includes second receiver, second transmitter, and second two-way communication device. The first communication apparatus or the second communication apparatus includes electric field strength detector. In a case where the first communication apparatus and the second communication apparatus are not connected to each other through two-way communication or electric field strength detected by the electric field strength detector is less than a predetermined value, the first communication apparatus stops a call function of the first transmitter or the second communication apparatus stops a wait function of the second receiver.