To easily switch the connection of light transmission lines, to realize remote control operation, to reduce the loss of transmission and to hardly cause deterioration by repetitive use by providing the device with a reflection mirror reflecting a light beam made incident from an incident port toward an emitting port.

The reflection mirror 5 is selectively positioned at the crossing point of respective incident optical axes 2A and an optical axis 3A emitted from one of the emitting ports 3 so as to totally reflect the laser light beam made incident from the incident port 2 toward the ports 3. Since the incident optical axis 2A is orthogonally crossed to the emitting optical axis 3A, the total reflection mirror 5 is arranged by being inclined by the angle of 45°. Thus, the connection of the light transmission lines on the incident side and on the emitting side can be switched only by switching the position of the mirror 5 without executing troublesome attaching and detaching operation executed in the case of a device using an optical connector. Besides, since it is enough that the mirror 5 is linearly driven, the remote control operation is facilitated.