A method is provided for collecting a small blood sample by painlessly puncturing a finger. When the skin of a human being is punctured by a needle or another device at the depth that does not exceed 0.5 mm, pain accompanying the puncture is diminished or decreased. Regardless of an error in the depth of the puncture, the depth of puncture must not exceed this depth. The puncture site is located on the dorsal surface of a finger, in the area from the finger joint (IP joint of thumb, DIP joint of fingers other than thumb) to the proximal nail wall and the area extending from the proximal nail wall to the lateral nail wall.