Abstract: A three-phase collected type optical current transformer having a common hermetically sealed container miniaturized in its radial direction. The common hermetically sealed container incorporating central conductors and optical current transformers corresponding to three phases has a branch tube or flange in its radial direction. The flange incorporates optical spacial transmission members for three phases which guide the signals sent from the optical current transformers through optical fibers to the exterior of the common hermetically container. The optical spatial transmission members are arranged collectively. The common hermetically sealed container, when it has a branching portion protruding in its radial direction at its end, incorporates no flange but a concentrated optical spacial transmission member for three phases at the end in the axial direction of the common hermetically sealed container having the branching member.