There is provided a storage layer (13) between storage layers (11), (15). The storage layer (13) produces a relatively large spherical aberration for a protection layer thickness error. Information is written to or read from the storage layer (13) with a beam of light having a second wavelength. Information is written to or read from the storage layers (11), (15) with a beam of light having a first wavelength (longer than the second wavelength). Accordingly, a multi-format optical storage medium is realized on which information can be recorded or reproduced with a single objective lens. Also, an optical pickup is realized which is capable of recording or reproducing information on the multi-format optical storage medium.