An apparatus for sensing a spin chuck for a spin coating unit includes a spin chuck which sucks a wafer with vacuum pressure to allow the wafer to be placed thereon, a rotary shaft which is rotated by driving of a motor below the spin chuck correspondingly thereto, and whose upper end is engaged with the spin chuck so as to interlock with the rotation of the spin chuck and a shaft guide shaped so as to surround a tubular stationary shaft of the spin chuck engaged with the rotary shaft. The apparatus further includes a sensing unit which senses whether or not the stationary shaft of the spin chuck is inserted into the shaft guide to a predetermined height a control unit which determines whether or not the spin chuck has been assembled normally from a signal sensed by the sensing unit and a notifying means which is controlled by the control unit to allow a user to recognize an assembled state of the spin chuck.