An electronic device comprising: a housing including a front plate (102; 320) facing in a first direction, a rear plate (380; 670) facing in a second direction opposite to the first direction, and a side member (310; 615) surrounding a space between the front plate (102; 320) and the rear plate (380; 670), at least a portion of the side member (310; 615) being formed of a metal material forming a side surface of the electronic device; a polymer member (617; 650) in contact with the portion of the side member (310; 615) that is formed of a metal material, wherein a through hole extending from the side surface of the electronic device is formed in the side member (310; 615) and extending through the portion of the side member (310; 615) that is formed of a metal material, the through hole extending in a third direction perpendicular to the first direction; a display (101; 330) arranged between the front plate (102; 320) and the rear plate (380; 670); wherein the side member comprises a first surface (615a; 617a) formed by the portion of the side member (310; 615) that is formed of a metal material and the polymer member (617; 650) and facing the rear plate, and a trench formed on the first surface (615a; 617a) and opened toward the rear plate; wherein a portion of the polymer member (617, 650) defines at least a portion of a sidewall defining the trench; and a mechanical button structure at least partially located in the through hole communicated with the trench; characterized in that the electronic device comprises a waterproof tape disposed on the first surface (615a; 617a) of the side member and provided to attach the rear plate and the side member. a housing including a front plate (102; 320) facing in a first direction, a rear plate (380; 670) facing in a second direction opposite to the first direction, and a side member (310; 615) surrounding a space between the front plate (102; 320) and the rear plate (380; 670), at least a portion of the side member (310; 615) being formed of a metal material forming a side surface of the electronic device; a polymer member (617; 650) in contact with the portion of the side member (310; 615) that is formed of a metal material, wherein a through hole extending from the side surface of the electronic device is formed in the side member (310; 615) and extending through the portion of the side member (310; 615) that is formed of a metal material, the through hole extending in a third direction perpendicular to the first direction; a display (101; 330) arranged between the front plate (102; 320) and the rear plate (380; 670); wherein the side member comprises a first surface (615a; 617a) formed by the portion of the side member (310; 615) that is formed of a metal material and the polymer member (617; 650) and facing the rear plate, and a trench formed on the first surface (615a; 617a) and opened toward the rear plate; wherein a portion of the polymer member (617, 650) defines at least a portion of a sidewall defining the trench; and a mechanical button structure at least partially located in the through hole communicated with the trench; characterized in that the electronic device comprises a waterproof tape disposed on the first surface (615a; 617a) of the side member and provided to attach the rear plate and the side member.