To provide a composite material reinforced by fibers composed of carbon and/or graphite and having low thermal expansion coefficient in facial direction and to provide a method for producing it.

This composite material composed of carbon and/or graphite- series fibers and a matrix of copper or a copper alloy is the one composed of carbon and/or graphite-series fibers and a matrix of copper or a copper alloy, and, as for the carbon and/or graphite-series fibers, the length thereof exceeds 40 μm, the aspect ratio and volume ratio lie in the range surrounded by the points A (4, 75), B (10, 75), C (30, 55), D (30, 25), E (20, 25) and F (4, 45) shown by the fig. 1, and, furthermore, they are oriented in the direction of the two-dimensional face at random. It has a low thermal expansion coefficient in the facial direction and is suitable as the material for a substrate for a semiconductor device.