An electronic device according to various embodiments disclosed herein may include: a housing, a speaker embedded in the housing, an acoustic duct configured to transfer an output from the speaker to a user, an external hole formed in the housing to be connected to outside the electronic device, an external sound duct configured to transfer a sound introduced through the external hole to the user, and a variable hole member comprising a variable opening disposed in at least one of the external hole and the external sound duct, wherein the variable hole member may include a conductive member comprising a conductive material configured to apply an electric signal, a ventilation hole configured to allow a sound transferred from the external hole to pass therethrough, and a deformable member comprising a deformable material configured to deform based on the electric signal to close at least a portion of the ventilation hole.