To provide a waterproof potentiometer which is improved in waterproofing performance.

This waterproof potentiometer 1 suppresses occurrence of a gap in a sealed section by inhibiting, as much as possible the occurrence of such a state that air tends to flow from the outside to the inside, or vice versa, via the sealed section, so as to inhibit communication of a housing space section 10 with the outside by suppressing the pressure fluctuations in the housing section 10, by noting that the pressure in the space section 10 fluctuates as the outside temperature changes. Consequently, sealability of the sealed section is improved. Based on this idea, the waterproofing performance of this potentiometer is improved, by suppressing the pressure fluctuation in the space section 10 as much as possible, by installing a lid section 12 to an opening 11 which communicates the space section 10 with the outside and constituting the lid section 12 of a diaphragm.