A bicycle treadle device comprises a treadle having an axial hole at a center portion thereof; at least one control block being installed at the treadle near the locking sheet; the control block being installed to the treadle; the control block being formed by a main ring; a first protrusion and a second protrusion being protruded from the main ring which has different sizes. By rotating the control block, it can be adjusted so that one of the main ring, the first protrusion and the second protrusion to resist against the front locking sheet of the locking sheet to adjust the expansion of the front locking sheet. Furthermore an adjusting unit is used to change the tightness of the elastic unit of the locking sheet.