A phosphor which has a main crystal phase having the same crystal structure as that of CaAlSiN3, wherein the phosphor satisfies conditions of a span value (d90−d10)/d50 of 1.70 or less and a d50 of 10.0 μm or less, as represented with d10, d50, and d90 on a volume frequency measured according to a laser diffraction method; wherein the d10, d50, and d90 on a volume frequency in a particle distribution measured are each a measured by loading 0.5 g of a phosphor into 100 ml of a solution of 0.05% by weight of sodium hexametaphosphate mixed in ion exchange water, and subjecting the resultant to a dispersing treatment for 3 minutes with an ultrasonic homogenizer at an oscillation frequency of 19.5±1 kHz, a chip size of 20φ, and an amplitude of vibration of 32±2 μm, with a chip placed at a central portion.