A pedal device with a shiftable stepping position for a percussion instrument is disclosed. In view of the problems in the prior art that the player feels discomfort when the angle of the footboard is not correct and that the instrument may have a worse pose, the invention provides a back bottom board under the pedal device that can rotate and adjust its side-shifting angles. By shifting the position of the back bottom board, the footboard is moved and fixed at a position preferred by the player. Therefore, the position of the footboard is adjusted according to the stepping position of the player. Therefore, the invention can avoid the player's discomfort and be disposed as desired.