A stroboscope is utilized as an input device of a golf game system (10), for example. The golf game system includes a game machine (12) as an information processing apparatus and a golf-club-shaped input device (14), and within a housing of the game machine, an imaging unit (28) is housed, and the imaging unit is provided with an image sensor (40) and an infrared-LED. By utilizing the infrared-LED, an infrared ray is intermittently emitted to a predetermined range of an upper portion of the imaging unit. Accordingly, the image sensor intermittently images a reflective body provided in the golf-club-shaped input device moving within the range. Such the stroboscope image processing of the reflective body enables calculation of a velocity, and so on as an input of the game machine.