A light source device includes: an excitation light source that emits excitation light having an energy density of 10 W/mm2 or more; and a phosphor layer that has phosphor particles embedded in the matrix. The phosphor particles include at least one selected from the group consisting of metal oxides represented by a following formula (1) and metal oxides represented by a following formula (2). Y3-x1-y1R1y1Cex1Al5-z1Gaz1O12  (1) Y3-x2-y2R2y2Cex2Al5-z2Scz2O12  (2) In the formula (1), R1 includes at least one selected from the group consisting of Gd and Tb, and x1, y1, and z1 satisfy 0.003≤x1≤0.03, 0≤y1≤2.1, and 0≤z1≤2.2, respectively. In the formula (2), R2 includes at least one selected from the group consisting of Gd and Tb, and x2, y2, and z2 satisfy 0.003≤x2≤0.03, 0≤y2≤2.1 and 0≤z2≤1.5, respectively.