An electric junction box, having a terminal portion positioned in the connector engagement portion and arranged perpendicular to a direction along which case members attach each other, which can be assembled easily without increasing the number of components and manufacturing cost is provided. Also, a power supply device having the above-described electric junction box is provided. The electric junction box includes: a box main body having a connector engagement portion and an upper case attached to a lower case in an overlapping relationship; and a bus bar received in the box main body. The lower case includes a bottom wall portion, a positioning wall and peripheral walls. The bus bar includes the terminal portion positioned in the connector engagement portion, a positioning plate portion and a mount portion. The peripheral wall includes a cutout portion allowing the positioning plate portion to move into and out from the lower case.