Provided is an inverter built-in brushless direct current (BLDC) motor, in which an inverter housing and a cover are coupled to each other by having a connector block interposed therebetween, a sealing portion formed in the connector block seals between a circumference in a height direction and a length direction of the connector block and an inner side surface of the inverter housing and the cover, and a space between an electric wire penetrating through an electric wire through hole and the connector block, thereby simplifying parts for forming a watertight structure, easily sealing between the inverter unit and the connector block and sealing between the connector block and the electric wire, and reducing a package size including a connector block assembling part formed in the inverter unit and the connector block.