A heat retaining device configured to retain a container containing a sample therein at a predetermined temperature, comprising: a supporting rod; a top plate mounted at an upper end of the supporting rod; a bottom plate mounted at a lower end of the supporting rod; a heat retaining body movable along the supporting rod; and a supporting spring (31; 33) provided between the heat retaining body and the bottom plate, wherein the heat retaining body includes a hole at an upper face thereof, the hole being configured to contain the container therein and having an inner face shaped corresponding to a shape of an outer face of the container, and a pressing force applied to the container contained in the hole of the heat retaining body compresses the supporting spring (31; 33) to move the heat retaining body downward along the supporting rod, and release of the pressing force moves the heat retaining body upward by an elastic force of the supporting spring (31; 33) until the heat retaining body comes into contact with the top plate, characterized in that the bottom plate is provided with a rod, and the heat retaining body includes an opening at a lower face thereof, the opening being connected to the hole at the upper face of the heat retaining body, the rod being disposed in the opening, and when the heat retaining body is moved downward along the supporting rod, the container contained in the hole of the heat retaining body comes into contact with the rod, thereby lifting the container from the hole of the heat retaining body, or the bottom plate is provided with a cam protrusion, and the heat retaining body includes an opening at a lower face thereof, the opening being connected to the hole at the upper face of the heat retaining body, and the cam protrusion being disposed in the opening, and when the heat retaining body rotates around the supporting rod, the container stored in the hole of the heat retaining body is lifted from the hole of the heat retaining body by a cam function between the cam protrusion and the container. a supporting rod; a top plate mounted at an upper end of the supporting rod; a bottom plate mounted at a lower end of the supporting rod; a heat retaining body movable along the supporting rod; and a supporting spring (31; 33) provided between the heat retaining body and the bottom plate, wherein the heat retaining body includes a hole at an upper face thereof, the hole being configured to contain the container therein and having an inner face shaped corresponding to a shape of an outer face of the container, and a pressing force applied to the container contained in the hole of the heat retaining body compresses the supporting spring (31; 33) to move the heat retaining body downward along the supporting rod, and release of the pressing force moves the heat retaining body upward by an elastic force of the supporting spring (31; 33) until the heat retaining body comes into contact with the top plate, characterized in that the bottom plate is provided with a rod, and the heat retaining body includes an opening at a lower face thereof, the opening being connected to the hole at the upper face of the heat retaining body, the rod being disposed in the opening, and when the heat retaining body is moved downward along the supporting rod, the container contained in the hole of the heat retaining body comes into contact with the rod, thereby lifting the container from the hole of the heat retaining body, or the bottom plate is provided with a cam protrusion, and the heat retaining body includes an opening at a lower face thereof, the opening being connected to the hole at the upper face of the heat retaining body, and the cam protrusion being disposed in the opening, and when the heat retaining body rotates around the supporting rod, the container stored in the hole of the heat retaining body is lifted from the hole of the heat retaining body by a cam function between the cam protrusion and the container.