To provide fluorescent substances improved in quantum efficiency, wavelength converters, light emitters and lighting installations.

The fluorescent substance includes an Eu-containing M13MgSi2O8 type crystal (M1 is Sr or Ba) as a primary crystal and an M12MgSi2O7 type crystal as a secondary crystal and satisfies 0.002B/(A+B)0.052, wherein A is the X-ray diffraction strength of a peak detected at 2=31.5-33 of the primary crystal and B is the X-ray diffraction strength of a peak detected at 2=28-30.5 of the secondary crystal. Such fluorescent substance can improve the quantum efficiency of blue-emitting fluorescent substances.