The invention relates to an action sensing device which comprises a containing part, an elastic cantilever, a piezoresistive transducer, a connecting part, a pneumatic-bearing slipper block and an infrared-light sensing module group. The containing part comprises a front panel and a back panel, which respectively comprise a big orifice in the middle of each panel and a plurality of small orifices evenly surrounding the big orifice. The elastic cantilever is positioned in the containing part and has a free end on which the connecting part is fixed. The pneumatic-bearing slipper block can be movably connected with the connecting part and is positioned in a connection range between the big orifice of the front panel and the big orifice of the back panel. The piezoresistive transducer adheres to the surface of the pneumatic-bearing slipper block. The infrared-light sensing module group is positioned on the front panel and can receive infrared light. With the action sensing device, air flow running through the orifices of the panels can enter the containing part and form laminar flow which strikes the pneumatic-bearing slipper block and leads the pneumatic-bearing slipper block to swing along the flowing direction of the laminar flow, and the piezoresistive transducer can sense the moving status of the pneumatic-bearing slipper block.