PURPOSE: To always hold the foot-operated position constant so as to improve operability by constituting a foot-operated type jack so that a screw shaft is rotated normally and reversely through first and second power transmission mechanisms selectively by repeating foot operation of a foot pedal, and a loading base is elevatably moved through a pantograph mechanism.

CONSTITUTION: When an operation lever of a selection mechanism provided along the upper part of a foot pedal 15 is operated to be on an ascent drive position (a descent drive position) and the pressing operation of the foot pedal 15 is repeated, the operation is converted to one way rotating motion of a first drive shaft 27 through a first power transmission mechanism 38 (a second power transmission mechanism 39), a screw shaft 20 is rotated through a bevel gears 29 (30) and 21 so as to lift (lower) a nut 23, and a loading base 14 is lifted (lowered) by approaching the rotational motion (separating rotational motion) of the link pair of a pantograph mechanism. In this case, the positions of the swing axis of the foot pedal 15, namely the first and second drive shafts 27, 28 are not changed, and hence the foot operating position of the foot pedal 15 is always constant and good operability can be obtained, regardless of the elevatable motion of the loading base 14.