The invention provides an electric junction box with an enhanced thermal insulation between neighboring part-receiving chambers without causing excessive increase in the size of a case. In order to attain the objective, there is provided an electric junction box, which includes a case provided with a case body, a lower cover coupled to the lower end of the case body, and first and second upper covers and coupled to the upper end of the case body. The case includes neighboring first and second part-receiving chambers and. A through-hole is located between the first and second part-receiving chambers and extends from an upper end of the case to a lower end of the case. The through-hole has an enlarging portion, which is disposed at a lower end thereof and has increasing cross-sectional area as approaching to the lower end of the through-hole.