A power converting device includes a first substrate, a driving module, and a converting module. The first substrate is inserted into a main plate. The first substrate has a first axial direction and a second axial direction perpendicular to the first axial direction, the second axial direction is perpendicular to the main plate. The driving module is located at one side of the first substrate and electrically connected to the first substrate. The converting module is located at the other side of the first substrate and electrically connected to the driving module. A length of the converting module is substantially equal to a length of the first substrate in the first axial direction, and a width of the converting module is smaller than the length of the first substrate in the first axial direction.