To realize the improvement of an interlaminar strength, which has a wide range of application and is low on cost and effective in the loading direction, by a method wherein a reinforcing pin made of shape-memory alloy is arranged at a part, at which a low interlaminar strength causes a trouble, under the condition that the reinforcing pin is compressively deformed at the forming and hardening of a laminate type composite material under heat.

A laminate type composite material 4 is produced from prepreg sheets, each of which is formed by arranging fibers to one direction in a polymer resin under semi-hardened state. On the other hand, a reinforcing pin 1, which has been elongated to the length L1, is arranged to the thickness of the plate of this material at a part, the interlaminar strength of the laminate type composite material 4 at which is wanted to be reinforced or a part, at which the interlaminar strength is requested. Next, by an ordinary composite material forming method, the laminate type composite material 4 is formed and hardened under heat. In this case, the reinforcing pin 1 is a straight pin and its shape is memorized. When the pin is made of Ni-Ti alloy, the pin is kept at about 500°C under the state that its shape is fixed. During the production of the structure of a composite material under the normal temperature, the reinforcing pin 1 is elongated axially under the condition that the strain given to the reinforcing pin 1 is 7% or less.