The present application provides a sensor capable of high-precision measurement with high SN ratio even when the ambient temperature changes, and a bandpass filter for the sensor. The sensor has a
light source, a bandpass filter that extracts light of a peak
wavelength of the
light source, and a light-receiving element that receives the light extracted by the bandpass filter. The bandpass filter has a bandpass layer and a support that supports the bandpass layer. When the
thermal expansion coefficient of the bandpass layer is α1, the
elastic modulus is E1, the
thermal expansion coefficient of the support is α2, and the
elastic modulus is E2, α1 > α2 and E1 < E2 are satisfied.