An information record medium is provided with: a first record layer (107) for recording first information, and one or more second record layers (207) disposed on said first record layer, each second layer being for recording second information, each layer of said second layers has a predetermined area (PCA1-1) where a power calibration is performed to detect an optimum recording power of recording laser beam transmitted through the first record layer and another layer of the second layers, said another layer positioned closer to said first record layer than said each layer, and in opposite areas (TA) of said another layer and said first record layer, said opposite areas being opposite to said predetermined area of said each layer of said second layers, a first absolute amount of at least one of width and depth of a groove is increased and thereby light transmittance in said opposite areas is approached to (i) light transmittance under an assumption that the first absolute amount is not increased and said another layer and said first record layer are in a recorded state, in comparison to (ii) light transmittance under an assumption that the first absolute amount is not increased and said another layer and said first record layer are in a non-recorded state.