the illustrated position in order to cool the dehumidification cooling plate 24 to a predetermined temperature a dehumidification peltier element 26 as a second cooler is arranged in contact with the dehumidification cooling plate 24 a heat dissipation fin 28 for the peltier element 2 is provided outside the sample storage 2 in order to feed air to the heat dissipation fin 28 for heat dissipation the heat dissipation fin 28 is arranged inside a duct 29 and a fan 31 for air feeding is provided in the duct 29 in order to control the temperature of the dehumidification cooling plate 24 a temperature regulation circuit 30 and a temperature sensor 32 are provided the temperature sensor 32 is embedded in the dehumidification cooling plate 24 or attached in contact with the dehumidification cooling plate 24 in order to detect the temperature of the dehumidification cooling plate 24 the temperature regulation circuit 30 takes in a temperature detected by the temperature sensor 32 and controls the amount of current supplied to the peltier element 26 so that the dehumidification cooling plate 24 has a predetermined temperature the dehumidification cooling plate 24 the peltier element 26 the heat dissipation fin 28 the temperature regulation circuit 30 and the temperature sensor 32 together constitute a second temperature regulation mechanism each of the sample cooling plate 4 and the dehumidification cooling plate 24 includes metal having a high thermal conductivity such as aluminum copper and stainless steel the sample cooling device of the present embodiment constitutes a sample injection device which is a liquid chromatograph autosampler therefore a sample inlet 35 for liquid chromatograph a sampling needle 34 for sucking.