To provide a foam composition having a small viscosity variation during foaming and capable of obtaining a uniform foam without a delicate temperature control.

The foam composition comprises a mixture of at least a foaming agent, an active hydroxy group containing liquid polymer material which may be cured at a lower temperature than a decomposition temperature of the foaming agent, and a curing agent containing an isocyanate group, wherein an equivalent ratio (NCO/OH) of the isocyanato group of the curing agent and the active hydroxy group of the liquid polymer material is 1.5 or lower. The foam composition is mixed at a room temperature, heated after forming to the decomposition temperature of the foaming agent or higher, and foamed to obtain a foam.