PROBLEM TO BE SOLVED: To set a switching point of a work mode changing with the passage of time when a worker performs a series of work using a work assisting device. SOLUTION: The operational physical amount (the operating force) applied by the worker and the physical amount (the object physical amount) concerning the movement of an object supported by a moving mechanism 12 are input to a physical data storage part 32 of a controller 14a of a work mode switching point setting device 10a. In clustering part 38, n-dimensional dot group taking n-number of physical amounts including the operational physical amount and the object physical amount is subjected to clustering. Clustering is performed including the operational physical amount, whereby the point group classified by each work mode with good accuracy. In a boundary setting part 40, a boundary surface for separating the point group belonging to the respective clusters in m-dimensional space is set, based upon the m-number of physical amounts obtained by subtracting the operational physical amount from n-number of physical amounts. The boundary surface is the switching point of a work mode. COPYRIGHT: (C)2007,JPO&INPIT