To eliminate the disadvantages that temperature measurement with a thermocouple is difficult in a small-sized sealing resin part since it is impossible to measure the temperature of the inside of the sealing resin even with an infrared thermometer and it is also impossible to determine an accurate temperature unless a coefficient of radiation is determined.

In a semiconductor light emitting device 10 including a semiconductor light emitting element 15, a sealing resin 11 of the semiconductor light emitting element 15, and electrodes 19 and 21 that supply electric power to the semiconductor light emitting element 15, the sealing resin 11 contains a cholesteric liquid crystal 16. From the reflection color of the cholesteric liquid crystal 16, the internal temperature of the sealing resin 11 is determined.