A pair of reinforcing ribs (50, 50) are formed on the bottom plate (33) of a box body (31) of an electrical component box (30). The reinforcing ribs (50, 50) have their respective pivot guides (50a, 50a) provided at their front ends to engage with associated pins (38b, 38b) on the safety cover (38). The safety cover (38) is pivotally supported to the pivot guides (50a, 50a) of the reinforcing ribs (50, 50) to allow it to open and close the opening of the box body (31).