A percussion device of a cajon includes a base with a bottom plate, two upright columns on the same side of the bottom plate, a pedal pivotally coupled to the bottom plate, a pivot horizontally pivoted to the top of the two upright columns, a hammer fixed to an outer segment of the pivot, a restoring tension spring for restoring the position of the pivot after rotation, a link member coupled between first and second ends of the pedal. When the second end of the pedal is stepped downward, the first end is warped to link the link member to rotate the pivot while stretching the restoring tension spring, and the hammer swings with the rotation of the pivot. After the pedaling force disappears, the restoring tension spring pulls the pivot to rotate and link the link member to swing the first end downward and restore its original position.