An accessory removably attachable to a camera body and including a plurality of terminals, the accessory comprising: a first terminal (LDET) for causing the camera body to detect that the accessory is attached thereto; a second terminal (VBAT) through which a first power supply voltage is supplied from the camera body; a third terminal (PGND) used for a ground potential for the first power supply voltage; a fourth terminal (V33) through which a second power supply voltage is supplied from the camera body; a fifth terminal (GND) used for a ground potential for the second power supply voltage; a sixth terminal (RDY) used to indicate whether or not communication with the camera body is allowed; an eighth terminal (CLK) that receives a first clock signal of a first cycle from the camera body; a seventh terminal (DATAB) that receives a first data signal in synchronization with the first clock signal from the camera body; a ninth terminal (DATAL) that outputs a third data signal to the camera body in synchronization with the first clock signal; a tenth terminal (HCLK) that outputs a second clock signal of a second cycle to the camera body, the second cycle being longer than the first cycle; and an eleventh terminal (HDATA) that outputs a second data signal to the camera body in synchronization with the second clock signal, wherein: three terminals of the third terminal, the fourth terminal and the fifth terminal are positioned between the second terminal and the sixth terminal; and three terminals of the seventh terminal, the eighth terminal and the ninth terminal are positioned between the sixth terminal and the tenth terminal. a first terminal (LDET) for causing the camera body to detect that the accessory is attached thereto; a second terminal (VBAT) through which a first power supply voltage is supplied from the camera body; a third terminal (PGND) used for a ground potential for the first power supply voltage; a fourth terminal (V33) through which a second power supply voltage is supplied from the camera body; a fifth terminal (GND) used for a ground potential for the second power supply voltage; a sixth terminal (RDY) used to indicate whether or not communication with the camera body is allowed; an eighth terminal (CLK) that receives a first clock signal of a first cycle from the camera body; a seventh terminal (DATAB) that receives a first data signal in synchronization with the first clock signal from the camera body; a ninth terminal (DATAL) that outputs a third data signal to the camera body in synchronization with the first clock signal; a tenth terminal (HCLK) that outputs a second clock signal of a second cycle to the camera body, the second cycle being longer than the first cycle; and an eleventh terminal (HDATA) that outputs a second data signal to the camera body in synchronization with the second clock signal, wherein: three terminals of the third terminal, the fourth terminal and the fifth terminal are positioned between the second terminal and the sixth terminal; and three terminals of the seventh terminal, the eighth terminal and the ninth terminal are positioned between the sixth terminal and the tenth terminal. three terminals of the third terminal, the fourth terminal and the fifth terminal are positioned between the second terminal and the sixth terminal; and three terminals of the seventh terminal, the eighth terminal and the ninth terminal are positioned between the sixth terminal and the tenth terminal.