Abstract: The present invention discloses a modular charging device and a cooling structure thereof. The modular charging device comprises a housing, at least one battery package socket located on the housing, and a PCB located in the housing, the at least one battery package socket being located at one or two sides of the PCB, at least one battery package being electrically connectable into the at least one battery package socket in a plug-in manner, and the battery package socket comprising a battery package insertion slot extending inwards from the housing to the PCB. A cooling structure for a modular charging device comprises an air inlet disposed at one end of a housing, an air outlet at another end, and a pathway between a first PCB and a second PCB, the fan causing an airflow to flow through the pathway.