A flow rate/liquid type detecting method for detecting the flow rate of a fluid and, at the same time, detecting any one of or both the type of the fluid and the concentration of the fluid, characterized in that, by using a flow rate/liquid type detecting apparatus comprising: a main passage through which a fluid to be detected flows, an auxiliary passage branched from the main passage, and a flow rate/liquid type detecting sensor device provided in the auxiliary passage, is provided, and in conducting any one of or both the detection of the type of the fluid and the detection of the concentration of the fluid, the auxiliary passage opening/closing valve is closed, and the fluid is allowed to temporarily stay within the flow rate/liquid type detecting sensor device to conduct any one of or both the detection of the liquid type and the detection of the concentration, and in detecting the flow rate of the fluid detected, the auxiliary passage opening/closing valve is opened to allow the fluid to flow into the flow rate/liquid type detecting sensor device to detect the flow rate.