Switch device and assembly method

A switch device comprising:

• an operation knob on which a sliding operation can be performed in a horizontal direction;
• a holder member configured to hold the operation knob and move in the horizontal direction integrally with the operation knob;
• a drive member configured to tilt as the holder member moves in the horizontal direction;
• a switch that is pressed down by the drive member as the drive member tilts;
• and
• a support member configured to support the holder member such that the holder member can move in the horizontal direction,
• wherein the holder member has a base that is provided at a center of the holder member in the horizontal direction and a flange that extends outward from the base in the horizontal direction, and
• wherein the support member has an upper wall that restricts a movement of the holder member in a vertical direction by contacting an upper surface of the flange, and a slit that is provided between the upper wall and a middle wall lower than the upper wall and that has a fixed vertical width.