An electrical junction box comprising: a casing configured to be mounted in a vehicle; a start electrical component (20, 20A) housed in the casing and to which a current is supplied at least at a start of the vehicle for controlling supply of current to a vehicle electrical component for starting the vehicle, the start electrical component (20, 20A) including an electrical component case and a terminal portion, the terminal portion being housed in the electrical component case and having a contact (FC, MC); an operational electrical component (14, 15, 20, 20B) housed in the casing and to which a current is supplied at least during an operation of the vehicle; and a surrounding heat shield wall disposed between the start electrical component (20, 20A) and the operational electrical component (14, 15, 20, 20B), wherein the casing houses a circuit board on which the start electrical component (20, 20A) and the operational electrical component (14, 15, 20, 20B) are mounted, and the circuit board has a circuit pattern connected to the terminal portion; the surrounding heat shield wall has a tubular shape having a bottom and an opening that opens toward the circuit board, and the surrounding heat shield wall surrounds the start electrical component (20, 20A); and the start electrical component (20, 20A) includes a plurality of start electrical components and the plurality of start electrical components (20, 20A) are mounted on the circuit board, and the surrounding heat shield wall includes a plurality of surrounding heat shield walls and the plurality of surrounding heat shield walls individually surround each of the start electrical components (20, 20A). a casing configured to be mounted in a vehicle; a start electrical component (20, 20A) housed in the casing and to which a current is supplied at least at a start of the vehicle for controlling supply of current to a vehicle electrical component for starting the vehicle, the start electrical component (20, 20A) including an electrical component case and a terminal portion, the terminal portion being housed in the electrical component case and having a contact (FC, MC); an operational electrical component (14, 15, 20, 20B) housed in the casing and to which a current is supplied at least during an operation of the vehicle; and a surrounding heat shield wall disposed between the start electrical component (20, 20A) and the operational electrical component (14, 15, 20, 20B), wherein the casing houses a circuit board on which the start electrical component (20, 20A) and the operational electrical component (14, 15, 20, 20B) are mounted, and the circuit board has a circuit pattern connected to the terminal portion; the surrounding heat shield wall has a tubular shape having a bottom and an opening that opens toward the circuit board, and the surrounding heat shield wall surrounds the start electrical component (20, 20A); and the start electrical component (20, 20A) includes a plurality of start electrical components and the plurality of start electrical components (20, 20A) are mounted on the circuit board, and the surrounding heat shield wall includes a plurality of surrounding heat shield walls and the plurality of surrounding heat shield walls individually surround each of the start electrical components (20, 20A).