The invention belongs to the technical field of numerically-controlled machine tools and particularly provides a cutter head cooling device capable of supplying a liquid during rotation of a cutter head. The invention aims to solve the problem that in the prior art, a water outlet in a knife rest cannot rotate and the connecting structure of a water inlet hole of the cutter head and the water outlet of the knife rest is complex. The cutter head cooling device provided by the invention comprises a first cooling channel arranged on the cutter head, a second cooling channel arranged on the knife rest and a rotating disc arranged on the knife rest, wherein the cutter head is rotatably mounted on the knife rest; an annular hole is formed in the rotating disc, a connecting ring capable of sliding axially is formed in the annular hole, and the connecting ring can communicate with the first cooling channel and the second cooling channel. According to the cutter head cooling device provided by the invention, axial movement of the cutter head is replaced by axial slip of the connecting ring, so that the structure is simpler, and the rotating disc is arranged, so that the cutter head rotating to any positions can communicate with the first cooling channel and the second cooling channel to cool the cutter head.