To improve a water-proofing function.

An electric wire connecting device includes: a shield shell 15 having a cylindrical connecting portion 19 with an opening for inserting an electric wire on one end side, and having a cap portion 17 which can be installed to a casing 1 on the other end side; a grommet 27 formed in a cylindrical shape by soft material, formed with an extended cylinder portion 31 in which an electric wire W1 can be inserted on one end side, and formed with a skirt portion 29 fitted in the shield shell 15 from the connecting portion 19 side and stuck and fastened to an outer peripheral surface of a stepped portion 16, on the other end side; and a grommet protection member 42 formed by harder material than that of the grommet 27, and attached so as to surround the skirt portion 29 from an outer peripheral side.