To downsize a large electrical connection box such as a junction block and to enable the mounting of a compact integrated fuse therein.
Internal circuits are accommodated in a casing comprised of a lower casing 10 and an upper casing 11, and are divided into large current circuits, medium current circuits and small current circuits. The large current circuits are constructed by a busbar 18, the medium circuits by wires 16 and cramping terminals 17, and the small current circuits by a flexible printed circuit (FPC) 19. A fuse box 13 into which a compact integrated fuse 14 is fitted is arranged on the upper surface of the FPC 19, and upstream and downstream contact surfaces of narrowly and parallelly arranged fusible elements 34 of the fuse 14 are connected with the wires 16 and the FPC 19, respectively.