A well plate is formed with a well for holding a subject to be sucked by a suction nozzle on an inner bottom part and storing liquid and, a clearance forming member for forming a clearance to allow the liquid to flow in a state where a tip part of the suction nozzle is inserted into and held in contact with the well is provided in the well. According to the present invention, the clearance enabling the liquid to flow is formed even in the state where the tip part of the suction nozzle is inserted into and held in contact with the well in sucking the subject held in the well by the suction nozzle. The suction nozzle can suck the liquid around through the clearance and the subject held in the well is efficiently sucked through the suction port along the flow of the sucked liquid.