An insulation inspection technique for allowing the occurrence of sparks to be detected more satisfactorily and allowing a board in which sparks have occurred to be more satisfactorily detected as being detective is provided. An insulation inspection apparatus detects a voltage induced between insulation inspection target wiring patterns by the application of a voltage during a time period from the start of the voltage application between the insulation inspection target wiring patterns to a predetermined time when the voltage between the insulation inspection target wiring patterns has stabilized. When a voltage drop due to sparks occurring between the insulation inspection target wiring patterns is detected during the time period, the board to be inspected is determined to be defective. In particular, supply current during the time period is set in accordance with the number of inspection points of an upstream wiring pattern of the insulation inspection target wiring patterns.