A wavelength-tunable interference filter comprising: a first substrate; a second substrate facing the first substrate; a first mirror provided at the first substrate; a second mirror provided at the second substrate and facing the first mirror via a first gap; a first electrode provided at the first substrate; a second electrode provided at the second substrate and facing the first electrode via a second gap; and a bonding part bonding the first substrate and the second substrate together, the first substrate including a moving part where the first mirror is arranged, as viewed in a plan view taken from a Z-direction heading from the first substrate toward the second substrate, a diaphragm part surrounding the moving part and holding the moving part in such a way that the moving part is movable in the Z-direction, and an outer circumferential part provided outside of the diaphragm part and having a larger thickness in the Z-direction than the diaphragm part, the diaphragm part including a planar part having a uniform thickness, as viewed in a cross-sectional view sliced along a plane parallel to the Z-direction, and a first slope part arranged between the planar part and the outer circumferential part and having a thickness in the Z-direction incrementing as it goes from the planar part toward the outer circumferential part, the first electrode being provided at least over a range from the planar part to the first slope part, of a surface of the first substrate facing the second substrate, with an outer edge of the first electrode, which is an edge opposite to the first mirror, being located at the first slope part, the bonding part being provided over a range from a part of the first slope part to the outer circumferential part, characterised in that: the first electrode is formed of an inner electrode arranged outside of the first mirror and an outer electrode arranged outside of the inner electrode, and a gap between the inner electrode and the outer electrode has a length of 0.2 mm or shorter. a first substrate; a second substrate facing the first substrate; a first mirror provided at the first substrate; a second mirror provided at the second substrate and facing the first mirror via a first gap; a first electrode provided at the first substrate; a second electrode provided at the second substrate and facing the first electrode via a second gap; and a bonding part bonding the first substrate and the second substrate together, the first substrate including a moving part where the first mirror is arranged, as viewed in a plan view taken from a Z-direction heading from the first substrate toward the second substrate, a diaphragm part surrounding the moving part and holding the moving part in such a way that the moving part is movable in the Z-direction, and an outer circumferential part provided outside of the diaphragm part and having a larger thickness in the Z-direction than the diaphragm part, the diaphragm part including a planar part having a uniform thickness, as viewed in a cross-sectional view sliced along a plane parallel to the Z-direction, and a first slope part arranged between the planar part and the outer circumferential part and having a thickness in the Z-direction incrementing as it goes from the planar part toward the outer circumferential part, the first electrode being provided at least over a range from the planar part to the first slope part, of a surface of the first substrate facing the second substrate, with an outer edge of the first electrode, which is an edge opposite to the first mirror, being located at the first slope part, the bonding part being provided over a range from a part of the first slope part to the outer circumferential part, the first electrode is formed of an inner electrode arranged outside of the first mirror and an outer electrode arranged outside of the inner electrode, and a gap between the inner electrode and the outer electrode has a length of 0.2 mm or shorter.