A driving device of caulking gun includes a housing, a driving assembly, a threaded rod, and a transmission assembly. The housing defines an axial direction. The driving assembly is disposed on the housing and includes a motor assembly and a driving gear. The motor assembly and the driving gear are linked-up to rotate simultaneously. The threaded rod is slidably disposed on the housing and is nonrotatable with respect to the housing. The threaded rod is formed with a spiral groove. The transmission assembly is arranged in the housing and includes a transmission sleeve and a plurality of abutting members. The transmission sleeve is sleeved onto the threaded rod and is radially formed with a plurality of through holes. The abutting members are received in the through holes respectively. The transmission sleeve and the driving gear are linked-up.