A 3-way switch for a gas-insulated apparatus includes a first connecting part and a second connecting part perpendicular to the first connecting part, a support conductor having a first guide hole perpendicular to the direction of the first connecting part and a second guide hole in parallel to the direction of the second connecting part, a disconnecting switch (DS) operating part slidably coupled to the first guide hole, an earthing switch (ES) operating part slidably coupled to the second guide hole such that the ES operating part is perpendicular to the disconnecting switch operating part, and a main lever, one end of which is rotatably coupled to the support conductor and the other end of which is eccentrically rotated and rotatably connected to the DS operating part and the ES operating part for linear sliding of the DS operating part and the ES operating part.