To provide a clocking system for a game for appropriately clocking time of each player with a simple structure.

A square-shaped loop coil 12 is appropriately arranged on a running lane on which a player runs. When a sine wave is supplied from a magnetic field generation device 11, the loop coil 12 generates an AC electromagnetic field on itself. A radio tag 20 is arranged so that a detection direction of one magnetic field detection coil becomes almost parallel to the running face and a detection direction of the other magnetic field detection coil becomes almost perpendicular to the running face and detects an electromagnetic field intensity distribution making the electromagnetic intensity small at the center on the loop coil 12. The radio tag 20 determines an arrival to a clocking line L from detection of an inflection point of the electromagnetic field to specify the time of the arrival as measured time. The radio tag 20 transmits the specified measured time, etc., to an information receiving device 13.