To provide a flow oil detection device capable of more precisely detecting the existence of oil flowing in a pipe according to the light receiving amount of light receiving element which may be affected by various factors.

The flow oil detection device comprises a light emission device 21 for irradiating the bent part Pc formed in a pipe P of light translucency, a light receiving element 22 for receiving the light transmitted through the bent part Pc of the pipe P irradiated with the light emission device 21 and outputting the signal corresponding to the received light amount, a process unit 100 for creating detection signal corresponding to the existence of the flow oil flowing through the bent part Pc of the pipe P by processing the signal from the light receiving element 22. The process unit 100 is composed of the 1st process circuit 110 for creating a variation signal representing the variation of the signal from the light receiving element 22, and the 2nd process circuit 120 for creating the detection signal from the variation signal.