To provide a method for producing a composite member by which the shape of a base material can be simplified and an operating process can be simplified and metal structure of the composite material after melting and solidifying can be made precise, and the development of defect, such as shrinkage hole, impurity in this metal structure of the composite material can be reduced.

When the heating is maintained in a heating furnace, the composite material 6 is melted in a melting space 10 and this molten material is filled up in a cavity 4 of the base material 1. When this molten state is held for a fixed time, this molten material of the composite material 6 is diffused from the surface into the inner part of the base material 1. Then, in the case of feeding cooling gas into a recessed part 5 for cooling by inserting an air-gun nozzle 12 into the recessed part 5 for cooling in the base material 1, the base material 1 is cooled from the center part toward the outer peripheral part, and in the melting space 10, the composite material 6 is cooled from the boundary side with the base material 1 toward the outer peripheral part and solidified. This composite material 6 is diffused and joined on the surface of the base material 1 with this solidification.