An assembly structure for a motor drive unit for converting an input power into an alternating current power suitable for driving a motor, including: a base case; a heat dissipation fan comprising a fan and a housing arranged outside the fan to fix the fan, the heat dissipation fan being disposed in an area of an upper portion of the base case; a heat sink comprising a base and at least one side face portion formed by extending vertically downward from both left and right ends of the base, the heat sink being disposed on one side of the heat dissipation fan on the base case; a middle base disposed on the heat sink, a power printed circuit board assembly disposed on the middle base; and a filter PCB assembly disposed over the power PCB assembly, the assembly structure comprising: at least one hook fixing portion disposed on an upper surface of the base case to correspond to a position of a front face portion of the housing; at least one hook support disposed on the upper surface of the base case to correspond to a position of a rear face portion of the housing of said heat dissipation fan; a first guide portion disposed on the upper surface of the base case to correspond to positions of a left side face portion and a right side face portion of the housing; and a hook engagement portion formed on an inner surface of each of the hook fixing portion and the hook support, wherein a hole corresponding to a shape of the hook engagement portion is formed in areas corresponding to the hook engagement portion on a front surface and rear surface of the housing. a base case; a heat dissipation fan comprising a fan and a housing arranged outside the fan to fix the fan, the heat dissipation fan being disposed in an area of an upper portion of the base case; a heat sink comprising a base and at least one side face portion formed by extending vertically downward from both left and right ends of the base, the heat sink being disposed on one side of the heat dissipation fan on the base case; a middle base disposed on the heat sink, a power printed circuit board assembly disposed on the middle base; and a filter PCB assembly disposed over the power PCB assembly, the assembly structure comprising: at least one hook fixing portion disposed on an upper surface of the base case to correspond to a position of a front face portion of the housing; at least one hook support disposed on the upper surface of the base case to correspond to a position of a rear face portion of the housing of said heat dissipation fan; a first guide portion disposed on the upper surface of the base case to correspond to positions of a left side face portion and a right side face portion of the housing; and a hook engagement portion formed on an inner surface of each of the hook fixing portion and the hook support, wherein a hole corresponding to a shape of the hook engagement portion is formed in areas corresponding to the hook engagement portion on a front surface and rear surface of the housing. at least one hook fixing portion disposed on an upper surface of the base case to correspond to a position of a front face portion of the housing; at least one hook support disposed on the upper surface of the base case to correspond to a position of a rear face portion of the housing of said heat dissipation fan; a first guide portion disposed on the upper surface of the base case to correspond to positions of a left side face portion and a right side face portion of the housing; and a hook engagement portion formed on an inner surface of each of the hook fixing portion and the hook support, wherein a hole corresponding to a shape of the hook engagement portion is formed in areas corresponding to the hook engagement portion on a front surface and rear surface of the housing.