An optical space transmission device includes: a first portion; and a second portion which is rotatably connected to the first portion and performs space transmission of signals using light between the first portion and the second portion. The device includes: a first light emitting and receiving module which is provided for the first portion and includes: a first light emitting element composed of a light emitting diode emitting first signal light modulated based on a signal transmitted from the first to second portion; and a first light receiving element receiving second signal light modulated based on a signal transmitted from the second to first portions; and a second light emitting and receiving module which is provided for the second portion and includes: a second light emitting element composed of a semiconductor laser emitting the second signal light; and a second light receiving element receiving the first signal light.