A CAN package light emitting device comprises a semiconductor laser 1 bonded on a sub mount 6 and a CAN package 2 for housing the semiconductor laser 1 bonded on the sub mount 6. The CAN package 2 comprises a fixing structure 3 for fixing the semiconductor laser at a predetermined position, and a cap 4 covering the semiconductor laser 1 fixed to the fixing structure 3. Vapor pressure of Si organic compound gas in the CAN package 2 is limited to or below 5.4.times.10.sup.2 N/m.sup.2 to prevent any deposit as thick as inviting characteristics deterioration from being formed on the light emitting portion of the semiconductor laser 1 within the guaranteed time of its proper operation.