To provide a new technology for solving a masking failure by a masking member, regarding an air leak test for blocking an opening in a surface of a workpiece with the masking member and detecting air leak from a part different from the opening.

This air leak test device blocks the opening 11 in the surface of the workpiece 1 with the masking member 21 and detects the air leak from a part different from the opening 11 in the workpiece 1. The air leak test device comprises a pressure sensor 21b for detecting pressure distribution related to the masking member 21, and a means for displaying the pressure distribution (pressure distribution arithmetic section 32 and display section 31).