In a three-dimensional multi-channel optical switch using biaxially movable mirrors, a mirror packing density is improved to support an increased number of channels. The three-dimensional optical switch comprises a fiber collimator array, and a first mirror array and a second mirror array disposed in close proximity to a beam emission surface of the fiber collimator array. The first mirror array has arranged thereon a plurality of first mirrors each having a single rotation axis and a plurality of first windows. The second mirror array has arranged thereon a plurality of second mirrors each having a single rotation axis orthogonal to the first rotation axis and a plurality of second windows. A beam emitted from a fiber collimator passes through the first window, reflects on a fixed mirror and a movable mirror in order, passes through the second window, and exits to the outside.