Provided is a mineral base oil that conforms to viscosity grades VG22 to VG100 as defined in ISO 3448 and exhibits a distillation curve with a temperature gradient Δ|DT| of distillation temperature between two points of 2.0 vol % and 5.0 vol % of distillation amount being 6.8° C./vol % or less. A vacuum pump oil containing the mineral base oil is excellent in vacuum characteristics and can conform to viscosity grades VG22 to VG100 as defined in ISO 3448.