An optical semiconductor device , comprising: a light-emitting layer having a first main surface (M1), a second main surface (M2) opposed to the first main surface (M1), and a side surface; a fluorescent layer (4; 4b) provided on the first main surface (M1) and containing phosphor particles, the fluorescent layer (4; 4b) having a third main surface facing the first main surface and a fourth main surface opposed to the third surface; a light-transmissive layer provided on the fourth main surface of the fluorescent layer (4; 4b) and made of a light-transmissive inorganic material; first and second metal portions formed on the second main surface (M2) and configured to cause a current for exciting the light emitting layer to flow through the light emitting layer , when a voltage is applied thereto; a sealing layer provided on the second main surface (M2), the sealing layer having a fifth surface facing the third main surface and a sixth surface opposed to the fifth surface, the sealing layer covering the side surface of the light-emitting layer and sealing in the first and second metal portions while leaving first ends thereof exposed to an outside of the sealing layer , and the first metal portion comprises a first electrode provided on the second main surface (M2), a first metal post provided on the first electrode and a first metal layer provided on the first metal post , the second metal portion (7b, 8b, 1 1b) comprises a second electrode provided on the second main surface (M2), a second metal post provided on the second electrode and a second metal layer provided on the second metal post , the first metal layer and the second metal layer form the first ends , and the first ends are left exposed at the sixth surface of the sealing layer . a light-emitting layer having a first main surface (M1), a second main surface (M2) opposed to the first main surface (M1), and a side surface; a fluorescent layer (4; 4b) provided on the first main surface (M1) and containing phosphor particles, the fluorescent layer (4; 4b) having a third main surface facing the first main surface and a fourth main surface opposed to the third surface; a light-transmissive layer provided on the fourth main surface of the fluorescent layer (4; 4b) and made of a light-transmissive inorganic material; first and second metal portions formed on the second main surface (M2) and configured to cause a current for exciting the light emitting layer to flow through the light emitting layer , when a voltage is applied thereto; a sealing layer provided on the second main surface (M2), the sealing layer having a fifth surface facing the third main surface and a sixth surface opposed to the fifth surface, the sealing layer covering the side surface of the light-emitting layer and sealing in the first and second metal portions while leaving first ends thereof exposed to an outside of the sealing layer , and the first metal portion comprises a first electrode provided on the second main surface (M2), a first metal post provided on the first electrode and a first metal layer provided on the first metal post , the second metal portion (7b, 8b, 1 1b) comprises a second electrode provided on the second main surface (M2), a second metal post provided on the second electrode and a second metal layer provided on the second metal post , the first metal layer and the second metal layer form the first ends , and the first ends are left exposed at the sixth surface of the sealing layer . <EOS>