A method ensuring that a CaMgSi2O6:Eu2+ blue light-emitting phosphor having high emission intensity can be produced in an industrially advantageous manner is provided. The production method includes a step of mixing a calcium source powder, a europium source powder, a magnesium source powder and a silicon source powder composed of silicon diimide powder or the like in a ratio producing a CaMgSi2O6:Eu2+ blue light-emitting phosphor, and a step of subjecting the powder mixture to heating at a temperature of 400 to 1,000° C. in an oxygen-containing gas atmosphere and then firing at a temperature of 800 to 1,500° C. in a reducing gas atmosphere.