To accurately measure the swimming speed and distance by providing a rotation detecting means for detecting the rotation of a rotor rotated by water flow with non-contact and displaying the swimming speed from the relation between the rotational cycle of a prescribed rotational speed found from its output and the swimming speed.

A swimming counter is provided with a rotor chamber 7 formed inside a base 4 of the counter main body and the rotor 9 is mounted therein. A water flow path 29 extending from a water flow hole 27 to a water flow hole 28 is formed so as to feed the water flow to the rotor 9. Two magnets are arranged at intervals of 180° in this rotor 9 and a lead switch actuated thereby is packaged on a printed circuit board assembly in the main body side. A pulse of a signal is output from the rotation detecting means for every rotation of the rotor 9, the rotation cycle of a prescribed rotational speed of the rotor 9 is calculated based on the signal, and the swimming speed is found from the relation between the rotational cycle of the prescribed rotational speed and the swimming speed so as to display on a display means.