The objective of the invention is to provide crystallized glass and a crystallized glass substrate. The crystallized glass or substrate is suitable for use in protecting members of optical devices and the like, has a high visible light transmittance, a good color balance and high strength and is prepared at a low cost. The objective of the invention is to provide the crystallized glass in which viscosity of matrix glass is low and the matrix glass is not liable to devitrify. The crystallized glass comprises, in terms of mol % on an oxide basis: 30.0-70.0% of an SiO2 component, 8.0%-25.0% of an Al2O3 component, 0-15.0% of a Na2O component, 0-25.0% of a MgO component, 0-30.0% of a ZnO component and 0-10.0% of a TiO2 component, the molar ratio [Al2O3/(MgO+ZnO)] is 0.5 or more and 2.0 or less, and a crystal phase comprises one or more selected from RAl2O4, RTi2O5, R2TiO4, R2SiO4, RAl2Si2O8 and R2Al4Si5O18.