PURPOSE: To prevent direction misdetection resulting from the investigation of only a narrow area and to speed up processing by efficient scanning with respect to the device and method for the line direction calculation of the fingerprint which detects the directions of rise lines or depression lines of the finger print so that the device and method are used for a fingerprint collation device.

CONSTITUTION: An N-directional scanning circuit 14 scans a binary-coded image in a binary-coded image storage device 13 in a direction N and a scanning line length measuring circuit 15 measures the length of a scanning line where the same picture element value succeeds. Segments which are shorter than a specific threshold value are excluded and the directions and lengths of other segments are recorded, dot by dot, in a dot information storage device 16. A dot line direction detecting circuit 17 calculates the local direction of each of the dots from the directions and lengths of segments crossing the dot.