PURPOSE: To correctly and quickly detect a human finger used as a direct input interface device by retrieving a deep local minimum corresponding to the front end of the finger in its direction.

CONSTITUTION: A video camera 2, an edge detecting unit 4, a Hough transformation calculating unit 6, a possibility retrieval unit 8, and a clustering unit 10 are provided. The human finger is read and is outputted as picture data in a form of two-dimensional pixel data, and the edge of the hand is detected based on each pixel data, The image line of the detected edge is converted into parameters in a parameter space and is suitably subjected to Hough transformation, and edge pixels are integrated in the parameter space to determine the direction of the finger. A deep local minimum corresponding to the front end of the finger is retrieved in this determined direction, and end points prescribing the front end of the finger are clustered to determine the front end of the human finger.