A computer-readable storage medium having stored therein an information processing program executable by a computer of an information processing apparatus for processing a signal supplied from an input device comprising a plurality of load sensors (364a to 364d) capable of detecting a load of a user stepping on the input device, the information processing program causing the computer to function as: load information acquisition means for repeatedly acquiring load information based on the signal supplied from the input device, wherein the load information is a collection of data indicating the total value of load values detected by the plurality of load sensors; center-of-gravity information acquisition means for repeatedly acquiring center-of-gravity information, based on the signal supplied from the input device, wherein the center-of-gravity information is a collection of data indicating the center-of-gravity position which is calculated based on the load values detected by the plurality of load sensors; center-of-gravity direction calculation means for calculating a direction in which the center-of-gravity moves based on a recent center-of-gravity position and a preceding center-of-gravity position, wherein a center-of gravity movement information is determined based on whether the center-of-gravity position is equal to or greater than a predetermined threshold value which depends on the center-of-gravity direction; load determination means for determining, based on the load information, whether or not an amount of change in the total value of the load values satisfies a first condition; and action determination means (S6, S7) for determining a predetermined action of the user on the input device, based on the direction in which the center-of-gravity moves obtained at a time when a result of the determination performed by the load determination means is affirmative. load information acquisition means for repeatedly acquiring load information based on the signal supplied from the input device, wherein the load information is a collection of data indicating the total value of load values detected by the plurality of load sensors; center-of-gravity information acquisition means for repeatedly acquiring center-of-gravity information, based on the signal supplied from the input device, wherein the center-of-gravity information is a collection of data indicating the center-of-gravity position which is calculated based on the load values detected by the plurality of load sensors; center-of-gravity direction calculation means for calculating a direction in which the center-of-gravity moves based on a recent center-of-gravity position and a preceding center-of-gravity position, wherein a center-of gravity movement information is determined based on whether the center-of-gravity position is equal to or greater than a predetermined threshold value which depends on the center-of-gravity direction; load determination means for determining, based on the load information, whether or not an amount of change in the total value of the load values satisfies a first condition; and action determination means (S6, S7) for determining a predetermined action of the user on the input device, based on the direction in which the center-of-gravity moves obtained at a time when a result of the determination performed by the load determination means is affirmative.