A resin leak detector includes a pressure sensor element and a leak determination unit. The pressure sensor element detects a pressure in a case cavity. That is, when resin leaks into a space between an upper circuit case and a lower circuit case, the pressure in the case cavity decreases temporarily. The decrease of the pressure in the case cavity is detected by the pressure sensor element based on comparison between a detected pressure and a predetermined lower limit. The resin leak into the upper and lower circuit case is detected without cutting an outer case of an electronic device such as an acceleration sensor or the like.