Most of human activities are based on the movement of both legs. Therefore, in order to analyze the mechanics of human activities, it is essential to record the force exerted by foot on the ground. For the purpose of this recording, a new apparatus was devised. The new recording element is the PIESO resistance effect of the semi-conductive crystalloid. The effect is that when an external force is applied to a crystalloid, it's potential resistance is changed in accordance with the magnitude of the force and is returned to the normal level when the external force is removed. This element is attached to a supporting stainless steel frame (10X15X5mm). Those frames are fixed in the parts of toe and heel of shoe. From them electrical changes are led to an oscilograph through a Wheaston's bridge. In the various activities such as walking, running, jumping and side stepping, the force exerted by foot could be presicely recorded using this apparatus. This new device will be applicable in the wide range of kinesiological studies.