PURPOSE: To inform a user of the frequency of brushing accurately and to instruct the user on correct brushing by providing a frequency detector which detects the movement of a toothbrush to the end part of the toothbrush and displaying the movement of the toothbrush.

CONSTITUTION: The frequency detector 2 is provided to the rear end of the grip of the toothbrush 1 detachably. The position of a metallic ball 4 in the housing 3 of the frequency detector 2 is specified by a metallic ring 5 and a pulse signal is generated every time the ball contacts an opposite conductor 6. Two detectors 2A and 2B arranged at right angles to each other and their outputs are connected to an arithmetic processing circuit. The arithmetic result of tooth brushing is displayed on a display part to instruct the user on the correct brushing and also generate materials for analyzing the relation between the wear state of the enamel of teeth and the extent of movement of the corresponding to toothbrush.