An information recording medium comprises a recording layer including a mixture of organic polysilane and oxo metallic phthalocyanine pigment. Information is recorded by adding heat or light to the recording layer. In a method for recording information onto the information recording medium, a decoloring reaction of oxo metallic phthalocyanine pigment is used which is caused by heating the recording layer to a temperature equal to or higher than a pyrolyzing point of organic polysilane.