To provide an individual contact state monitoring device that has space-saving and low-cost features by reducing the number of parts and wiring material.

A plurality of composite circuits H1 to Hn which are series connections of contacts S1 to Sn and switch circuits K1 to Kn which are series connections of first electronic switches E1a to Ena closed by first applied voltages V1a to Vna and second electronic switches E1b to Enb opened by second applied voltages V1b to Vnb, are connected in parallel to a pair of transmission lines L. The transmission lines are connected with a reception circuit 1 comprising a voltage generation circuit 11 for generating the first and second applied voltages, a current detection circuit 12 for measuring a current flowing in the transmission lines, and a contact state detection circuit 13 for detecting opened/closed states of the contacts in synchronism with the voltage generation circuit and the current detection circuit.