BUCKLE AND SEAT BELT DEVICE

A buckle includes a supporting member, a case, a lock portion and an illuminating unit. The case covers the supporting member. The lock portion is supported by the supporting member and is covered by the case to lock or unlock a tongue which is inserted into an insertion hole. An insertion hole is formed between the case and the lock portion. The illuminating unit illuminates both ends of the insertion hole of the tongue. The illuminating unit includes a light emitting unit, a light distribution unit, a first diffusing unit and a second diffusing unit. The light emitting unit emits light. The light distribution unit distributes the light emitted by the light emitting unit to form a first light beam and a second light beam. The first diffusing unit diffuses the first light beam. The second diffusing unit diffuses the second light beam.