An input direction determination system includes an input direction determination section that determines the input direction based on a reference point and the indication position, and a reference point change section that determines whether or not to change the reference point based on an angle formed by a first direction that is determined by the reference point and an indication position at a first timing or a timing that precedes the first timing, and a second direction that is determined by the indication position at the first timing and an indication position at a second timing that follows the first timing, or an angle formed by connection lines that connect indication positions at different timings, and changes the reference point.