A start timing instructing device includes a sensor attachable to the body of a player to detect changes in angle and/or acceleration associated with a backswing movement of the player. A variable resistor sets a start timing associated with a predetermined angle and/or acceleration data and has a volume by which the set start timing is adjustable. A microprocessor calculates an angle and/or acceleration data of the backswing movement based on the detected angle and/or acceleration and generates a start timing instruction if the calculated angle and/or acceleration data meet the angle and/or acceleration data which have been set and adjusted through the variable resistor and the volume. The microprocessor controls a stimulator attached to the body of the player to generate a vibration, sound or electric stimulation upon receiving the start timing instruction so as to inform the player of the body start timing for the downswing.