Abstract: The present invention is to provide a heat sink used for a portable information processing apparatus, the casing of which has a recess in which an exchangeable arithmetic processor is accommodated. There is provided a heat receiving plate closely coming into contact with the arithmetic processor. The heat receiving plate includes a round hole portion arranged at one end. A heat pipe is inserted into the round hole portion. A fixing member is attached to the heat receiving plate at an outlet portion of the heat pipe arranged in the round hole portion. The heat receiving plate is fixed to the casing through the fixing member so that a hinge mechanism can be formed by the heat receiving plate and the heat pipe which is used as a fulcrum. At least a portion of the heat pipe is thermally connected with a radiating member.