Abstract: A method of manufacturing strain-detecting devices is provided. First, plural cylindrical substrates, each of which has one end closed by a diaphragm, are fixedly placed at predetermined positions of a fixing plate. A positioning marker is previously given to the fixing plate. The fixing plate having the substrates is then assembled into a jig. The jig sustains the substrates so that an outer surface of the diaphragm of each substrate is held at the same level. Through positioning the substrates, all the diaphragms are then positioned in place in a plane direction of the fixing plate with reference to the positioning marker. A strain gage portion is simultaneously formed on each of all the diaphragms. The fixing plate is then disassembled from the jig. In this step, the substrates with the strain gage portions, i.e., strain-detecting devices, are separated from the fixing plate.