To provide an optical pressure sensor having high accuracy and not requiring a wide area and also not being influenced by a loss accompanying the transmission of an optical signal, by using a contactless pressure sensor which is not electrical.

Plural optical couplers are connected to an optical transmission cable 16 with intervals placed and a partial signal is taken out form a pulse signal at the connection place. When a pulse optical signal transmits along the cable 16 and enters an array of an optical pressure sensor 22, plural couplers are respectively provided with an optical splitter, the sensor 22 and non pressure sensitive reflector 26, and non overlap signal pairs 30a to 30c are returned to the cable 16. The signal pairs 30a to 30c are inputted to a processor, and an intensity ratio of a pressure presentation signal 24 and a reference signal 28 which are included in the pairs 30a to 30c till here respectively is calculated. With this, because noise and loss can be compensated by using the signal 28, it is possible to acquire accurate pressure measurement value regardless of the position of the pressure sensor.