A microchip which comprises: a resinous base having a plurality of fine channels formed on one side thereof, one or more cylindrical parts disposed so as to protrude from the other side, and a through-hole which pierces each cylindrical part along the axis thereof and communicates with the fine channel so that the diameter of the inner wall of the through-hole gradually decreases from the tip end of the cylindrical part toward the fine channel at a first inclination angle; and a resinous covering member bonded to that side of the resinous base on which the fine channels have been formed. The microchip has been configured so that a liquid sample can be introduced from the tip end of each cylindrical part through the through-hole. The wall thickness of the cylindrical part on the end side where a liquid sample is to be introduced has been made smaller than the wall thickness thereof on the base side where the cylindrical part has been formed, by forming a step therebetween.