The present invention provides a blue phosphor having high luminance and showing less luminance degradation during driving of a light-emitting device. The present invention is a blue phosphor that includes: an alkaline earth metal aluminate represented by a general formula aBaO.bSrO.(1−a−b)EuO.cMgO.dAlO3/2, where 0.70≦a≦0.95, 0≦b≦0.15, 0.95≦c≦1.15, 9.00≦d≦11.00, and a+b≦0.97 are satisfied; and 0.008 mol to 0.800 mol of MWO4 with respect to 1 mol of the aluminate, where M is at least one element selected from a group consisting of Ba, Sr, and Ca.