An input device for an electronic apparatus includes a rotary dial module and a keypad surrounding the rotary dial module. The rotary dial module includes a base plate, a flexible printed circuit board, a retainer, a rotary dial, and a plurality of contacts. The flexible printed circuit board is mounted on the base plate. The retainer is positioned above the flexible printed circuit board and is mounted on the base plate. The rotary dial is rotatably mounted on the retainer. The contacts are mounted on the flexible printed circuit board. Each of the contacts is assigned to a portion of the rotary dial and capable of forming a closed circuit when the corresponding portion of the rotary dial is pressed down and in contact with the contact. The input device has a compact size because the rotary dial can replace some keys.