A cooling apparatus (10) for electronic device comprises an electronic element unit (11) which comprises a base member (14), a thermal conductive electric insulating layer (15) soldered to the base member (14) and a plurality of electronic elements (16) soldered to the thermal conductive electric insulating layer (15); at least one cooling unit (12) which is detachably kept in pressure contact with the base member (14) of the electronic element unit (11) and comprises a cooling block (19), at least one heat pipe (21) having a refrigerant (22) sealingly contained therein and inserted in the cooling block (19) at one end thereof and a plurality of radiation fins (23) provided at the other end of the at least one heat pipe (21); and a device (13) which serves to detachably keep the electronic element unit (11) and the cooling unit (12) in pressure contact with each other. The other end of the heat pipe (21) extends obliquely with a predetermined angle (α) with respect to the inserted portion thereof.