PURPOSE: To prevent an IC from having leakage due to dew condensation by providing a cover which covers an IC conveyance path and forming an entrance chamber communicating with a thermostatic chamber, providing a heater below and outside the entrance chamber, and holding its part above the room temperature.

CONSTITUTION: The thermostatic chamber 2 adjoins to a thermostatic chamber wall 2a which has an entrance opening 2b for ICs, the cover 6 which covers a chute rail 4 is provided outside the thermostatic chamber 2, and the entrance chamber 7 which communicates with the thermostatic chamber 2 is formed of the cover 6. This cover 6 is so shaped not to interfere with ICs 1 (1aW1f) during conveyance. The heater 8 is installed under the rail 4 at the part (G-H section) where the rail 4 passes the entrance chamber 7, and the rail in this section is controlled to temperature higher than the room temperature. Consequently, the temperature in the entrance chamber 7 formed of the cover 6 is raised and even when the inside of the thermostatic chamber is cooled to about -40°C, dew is prevented from being condensed in the entrance chamber 7. Therefore, the ICs are prevented from having leakage due to dew condensation.