A non-contact probe (2, 2A), comprising: an emitting element that radiates light with a spectral characteristic; a light receiving element that has a spectral characteristic comprising the spectral characteristic of the emitting element and that receives the light radiated from the emitting element to output a signal, the non-contact probe (2, 2A) detecting an object without contact based on the signal; and an optical filter that covers an optical path to the light receiving element, the optical filter having a spectral characteristic comprising a transmission band in which the filter transmits the light and a blocking band in which light to which the light receiving element is sensitive is blocked, wherein the transmission band comprises the spectral characteristic of the emitting element and a part of the spectral characteristic of the light receiving element, the blocking band comprises the spectral characteristic of the light receiving element outside the transmission band, and wherein the spectral linewidth of the spectral characteristic of the optical filter is set to be broader than and to comprise the spectral linewidth of the spectral characteristic of the emitting element and is narrower than and comprised in the spectral linewidth of the spectral characteristic of the light receiving element, characterized in that the optical filter comprises a light-incident surface and a light radiation surface parallel to each other, the light-incident surface and the light radiation surface being disposed to be inclined to a plane orthogonal to an optical axis of the light receiving element, a refractive index of a space from the optical filter to the light receiving element and a space surrounding the optical filter is 1, and a distance t between the light-incident surface and the light radiation surface of the optical filter is designed to satisfy a relation of formulae below when an angle between the optical axis of the light receiving element and a normal line of the light-incident surface is denoted by i, a refractive index of the optical filter is denoted by n, and a distance from the optical axis of the light receiving element to the farthest point in which the light receiving element receives light is denoted by d, wherein the formulae are: t < d ⋅ cos r / sin i − r and r = asin sin i / n an emitting element that radiates light with a spectral characteristic; a light receiving element that has a spectral characteristic comprising the spectral characteristic of the emitting element and that receives the light radiated from the emitting element to output a signal, the non-contact probe (2, 2A) detecting an object without contact based on the signal; and an optical filter that covers an optical path to the light receiving element, the optical filter having a spectral characteristic comprising a transmission band in which the filter transmits the light and a blocking band in which light to which the light receiving element is sensitive is blocked, wherein the transmission band comprises the spectral characteristic of the emitting element and a part of the spectral characteristic of the light receiving element, the blocking band comprises the spectral characteristic of the light receiving element outside the transmission band, and wherein the spectral linewidth of the spectral characteristic of the optical filter is set to be broader than and to comprise the spectral linewidth of the spectral characteristic of the emitting element and is narrower than and comprised in the spectral linewidth of the spectral characteristic of the light receiving element, characterized in that the optical filter comprises a light-incident surface and a light radiation surface parallel to each other, the light-incident surface and the light radiation surface being disposed to be inclined to a plane orthogonal to an optical axis of the light receiving element, a refractive index of a space from the optical filter to the light receiving element and a space surrounding the optical filter is 1, and a distance t between the light-incident surface and the light radiation surface of the optical filter is designed to satisfy a relation of formulae below when an angle between the optical axis of the light receiving element and a normal line of the light-incident surface is denoted by i, a refractive index of the optical filter is denoted by n, and a distance from the optical axis of the light receiving element to the farthest point in which the light receiving element receives light is denoted by d, wherein the formulae are: t < d ⋅ cos r / sin i − r and r = asin sin i / n