A connection structure of an electrical junction box includes: a first housing which is fixed to a vehicle and in which a through hole is formed; and a terminal block that is inserted into the through hole, has a conductor, and is supported by the first housing, wherein the conductor includes a first terminal portion placed on one side of the through hole in a penetrating direction in which the through hole penetrates the first housing, and a second terminal portion that protrudes from the first housing toward the other side in the penetrating direction and that is connected to an electric wire.