Provided is an electrical junction box including a lower case and an upper case joined to the lower case, wherein the upper case includes an inner wall that opposes an inner surface of the lower case and an outer wall that opposes an outer surface of the lower case, the outer wall has a first wall portion that is in intimate contact with the outer surface of the lower case and a second wall portion that extends upward continuously from the first wall portion, and an upper end of the lower case is inserted between the inner wall and the second wall portion with clearances CL1 and CL2.