An electronic apparatus, such as a blade server or the like, has a cooling system for efficiently cooling a plurality of heat generating semiconductor devices, such as a CPU, mounted on blades which is freely put on and taken off. The cooling system includes a thermosiphon which transfers heat from devices having relatively high heat generation, such as CPU or the like, to the outside of the apparatus, heat pipes which transfer heat of devices having relatively low heat generation to the thermosiphon, a thermal highway which is thermally coupled to the thermosiphon by the mounting of blades into a housing and collects and transfers the heat from the thermosiphon and the heat pipes, and a condenser which transfers the heat collected and transferred by the thermal highway outside a housing.