The utility model provides an electric power conversion device which is to guarantee a cooling effect on a plurality of heating components. A first concave pit (11) for accommodating DC reactors (DCL) and a second concave pit (12) for accommodating AC reactors (ACL) are formed in a frame body (10), a gap (H) in left and right direction being formed between the first concave pit (11) and the second concave pit (12). First cooling fins (F1), second cooling fins (F2) and third cooling fins (F3) corresponding to a switch element (IPM), the first concave pit (11) and the second concave pit (12) respectively are arranged on the outer side of the frame body. The switch element is arranged at the upper side of the gap (H). The first concave pit is arranged at the lower side of the second concave pit. The first cooling fins are almost vertical from the upper side of the frame body to the lower side, and the lower ends of the fins extend near the second concave pit. The second cooling fins and the third cooling fins are almost parallel with the first cooling fins; the upper ends of the second cooling fins and the upper ends of the third cooling fins extend to the positions of the first cooling fins on the upper side of the frame body; and the frame body is equipped with a fan (FAN) blowing from the lower side of the first cooling fins to the first cooling fins.