Provided is an electronic lock which achieves improved productivity while maintaining the performance of waterproofness for an internal electronic circuit of an insertion portion for a mechanical lock. Specifically provided is an electronic lock provided with a portable machine (1) which contains an electric circuit that locks and/or unlocks a door by communicating with the outside wirelessly, and a mechanical lock which is attachable to and detachable from the portable machine (1) and mechanically locks and/or unlocks the door. In the electronic lock, the portable machine (1) comprises: an upper case (10) and a lower case (20) which house the electric circuit; an inner case (30) within the upper case (10) and lower case (20), in which the electric circuit is disposed; an insertion portion (21) within the lower case (20), into which the mechanical lock is insertable from the front end thereof and which has an opening (23) in the upper surface (22) at the terminal end thereof; and a rubber member (24) which is inserted into the opening (23) of the insertion portion (21).