A circuit board, including a plurality of wiring lines extending along a first direction and arranged side by side along a second direction perpendicular to the first direction; a plurality of pads having a predetermined length along the first direction, the plurality of pads being on the wiring lines; ground pad outside the pads, the wiring lines including first wiring lines delivering a positive polarity signal and second wiring lines delivering a negative polarity signal, the pads including first pads on the first wiring lines and second pads on the second wiring lines, and a cross-sectional area of each wiring line being substantially equal to that of each pad.