To provide a cardiotachometer and its attachment method for reliably obtaining accurate cardiac potential signal from a human body by sufficiently securing electrical conductivity between a human body surface and an electrode without making a person to be measured feel uncomfortable.

In the cardiotachometer 1, a belt 20 is connected to a measurement part 10 to have a pipe 17 on the body 11 side communicate with a pipe 24 on a belt 20 side, so that liquid can be supplied. At the same time, a connection terminal 15 on the body 11 side and a connection terminal 25 on the belt 20 side are electrically connected to each other, and heart rate data become detectable. Moreover, by pressing a pressing part 13 provided to the measurement part 10, liquid stored in a tank 12 is supplied to an electrode 30 via the pipe 17 and the pipe 24 to reduce electric resistance between the human body surface and the electrode 30, and electrical conductivity is sufficiently secured.