To provide an insulation film which is formed on the surface of a capacitance type moisture sensor and satisfies conditions of (1) having a constant thickness over the whole surface of a substrate constituting the sensor, (2) having no pinholes, (3) having a strength, and (4) having no thin parts at a part of a corner of a detecting pattern, a part of a corner of a through-hole, or the like.

The capacitance type moisture sensor is formed by pressure-forming the entire surface of a plate-like body 7 formed by impregnating an insulating base material 5 with an insulating resin 6 to overlie the front side of an insulating substrate 1 which has the detecting patterns 2, 2' of a conductive body constituting an element of the capacitance type moisture sensor on the front side and connecting patterns 3, 3' of the conductive body on the rear side through the though-hole 4 and by forming a hardened insulating film 8.