Abstract: Provided is a microchip having a protrusion to which a device for introducing or discharging a liquid sample, a device for causing the liquid sample to flow, or another device is connected, the protrusion retaining strength. The microchip includes a resin substrate (2) which has a fine flow channel (3), a penetrated hole (6) communicating with the fine flow channel (3), and a protrusion (5) formed so as to surround the penetrated hole (6) and project in the thickness direction. The protrusion (5) has a wall thickness (W) and a height (T) satisfying the relationship (T/10)?W?(T/2).

Abstract: 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.