A phosphor and a light emitting device including the phosphor may be provided that emits light having a peak wavelength between a green wavelength band and a yellow wavelength band, has a crystal structure of which the chemical formula is MSi2N2O2, M=CaxSryEuz (x+y+z=1), and has a triclinic system crystal structure in which, when molar ratios of Ca, Sr and Eu are x, y and z respectively, x+y+z=1 and when the x, y and z are represented by a triangular projection, the x, y and z are distributed on the lines and at the inside of an area formed by connecting five points of (0.45, 0.55, 0), (0.75, 0.25, 0), (0.75, 0, 0.25), (0.5, 0, 0.5) and (0.45, 0.05, 0.5) by a solid line on a triangular diagram.