To provide a contact information input circuit having decreased power consumption, even by a constitution in which many input contacts are connected and further reduced in the size of a circuit scale than prior art.

In the contact information input circuit 1, signal input terminals for connecting external input contacts are divided into sets into 8 groups, each of eight points, and the input contacts of each set are respectively connected to 8 photocouplers A1 to A8. A voltage applied to confirm on/off states of each input contact is sequentially switched and applied at each predetermined time by photo-MOS relays B1 to B8 of voltage switching circuits. The signal input via the photocoupler at a voltage applying time to each set is transmitted from a data input circuit 21 to a CPU 41. As an operation conforming circuit for confirming the operations of each of the photocouplers A1 to A8 and the photo-MOS relays B1 to B8, photocouplers C1 to C8, diodes TD1 to TD8 and a photo-MOS relay B9 are provided, and the reliability of the input circuit 1 is improved.