In order to investigate the effects of heat treatment on the thermoelectric motive force (EMF) of type R thermocouples, the changes of EMF in the freezing points of aluminum and silver cells were measured with the immersion depth of themocouples. With the variation of heat treatment methods before use, it was found that the EMF values were different from each other, maximum $17.1{mu}V$ at $660.323^{circ}C$ and $18.1{mu}V$ at $961.78^{circ}C$. Additionally a thermocouple, which was not heat-treated fully, showed an EMF difference with the immersion depth even though it was located on the region maintained at the constant temperature. The measured differences were about maximum $7.8{mu}V$ at the Al freezing point and $18.9{mu}V$ at the Ag freezing point. It was recongnized that a thermocouple for the precise temperature measurement should be heat-treated carefully before service. In this report, the proper heat treatment methods for the type R thermocouple were given on the basis of the obtained experimental results.