To provide a sample preparing device which contains many wells and with which the measurement of a very small amount of substance requiring the injection and discharge of a liquid, etc., can be carried out in a short time.

This sample preparing device is composed of a substrate provided with a plurality of units. Each of them is composed of a plate having a plurality of through wells, and provided with a liquid supply section at one end and porous films arranged in the bottom sections of the wells, so that the films may be separated from the plate. A sucking mechanism sucks liquids supplied to the wells from the liquid supplying sections toward the bottom sections of the wells.