PURPOSE: To measure blood pressure and to display its result by only operating one switch by providing a single switch means for instructing power supply from a power source and its stop, and also, a start, and an end of measurement by a measuring means.

CONSTITUTION: In a power source switch circuit 215, when an output switch 104 of a one-shot circuit 301 is depressed, a pulse signal 307 of prescribed width is outputted only once. This signal passes through a NAND circuit 303 and is inputted to a clock terminal of a flip-flop 305. As for the flip-flop 305, when a battery is installed, its Q output becomes a low level. In such a state, when the switch 104 is depressed, the Q output is varied from a low level to a high level, a PNP transistor 306 is turned on and power is supplied to a circuit of the main body. Also, when an electronic sphygmomanometer is not operated for about three minutes and 30 seconds, a CPU of the main body outputs a control signal 216, the flip-flop 305 is inverted and the PNP transistor 306 becomes a turn-off state, and the power supply is cut off.