To provide a compact chirped mirror capable of performing fine dispersion compensation for ultrashort light pulse and the like such as femtosecond light pulse and suppressing losses of the ultrashort light pulse due to the dispersion compensation, and to provide a chirped mirror unit including the chirped mirror and easily performing dispersion compensation.SOLUTION: The chirped mirror is configured such that a group velocity delay dispersion GDD value at a center wavelength within a prescribed wavelength region is a function of incidence angle θ, and monotonously increases or monotonously decreases within a prescribed incidence angle region. The chirped mirror unit includes the chirped mirror and a chirped mirror rotation mechanism relatively rotating the chirped mirror with respect to an incident optical path.SELECTED DRAWING: Figure 38
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