A circuit board, comprising: a signal layer, wherein the signal layer comprises at least one set of differential wires, and the at least one set of differential wires comprises a first differential wire and a second differential wire that are insulated from each other; the first differential wire comprises a first part, a second part, and a third part that are arranged successively in an extension direction of the first differential wire; and the second differential wire comprises a fourth part, a fifth part, and a sixth part that are arranged successively in an extension direction of the second differential wire; and a ground plane, wherein the ground plane is disposed on at least one side of the signal layer, and is insulated from the signal layer; and the ground plane is provided with a first hollowed-out portion, and an orthographic projection of the first hollowed-out portion on the signal layer overlaps with the second part and the fifth part, wherein the ground plane is further provided with a second hollowed-out portion and a third hollowed-out portion; an orthographic projection of the second hollowed-out portion on the signal layer is located on one side that is of the first differential wire and that is away from the second differential wire; an orthographic projection of the third hollowed-out portion on the signal layer is located on one side that is of the second differential wire and that is away from the first differential wire; and the first hollowed-out portion, the second hollowed-out portion and the third hollowed-out portion continuously penetrate through the ground plane; and the ground plane is enclosed by the first hollowed-out portion, the second hollowed-out portion and the third hollowed-out portion into a first branch and a second branch, and the first branch and the second branch are respectively disposed on opposite sides of the first hollowed-out portion; and an edge of the first branch and an edge of the second branch are flush with edges of the second hollowed-out portion and the third hollowed-out portion, wherein a length range of the first branch and the second branch is a ratio of a wavelength at a target frequency to 4; the length of the first branch is a length from an edge that is of the first branch and that is away from the second branch to the first hollowed-out portion, the length of the second branch is a length from an edge that is of the second branch and that is away from the first branch to the first hollowed-out portion, and the target frequency is a frequency of a common mode signal attenuated by the circuit board. a signal layer, wherein the signal layer comprises at least one set of differential wires, and the at least one set of differential wires comprises a first differential wire and a second differential wire that are insulated from each other; the first differential wire comprises a first part, a second part, and a third part that are arranged successively in an extension direction of the first differential wire; and the second differential wire comprises a fourth part, a fifth part, and a sixth part that are arranged successively in an extension direction of the second differential wire; and a ground plane, wherein the ground plane is disposed on at least one side of the signal layer, and is insulated from the signal layer; and the ground plane is provided with a first hollowed-out portion, and an orthographic projection of the first hollowed-out portion on the signal layer overlaps with the second part and the fifth part, wherein the ground plane is further provided with a second hollowed-out portion and a third hollowed-out portion; an orthographic projection of the second hollowed-out portion on the signal layer is located on one side that is of the first differential wire and that is away from the second differential wire; an orthographic projection of the third hollowed-out portion on the signal layer is located on one side that is of the second differential wire and that is away from the first differential wire; and the first hollowed-out portion, the second hollowed-out portion and the third hollowed-out portion continuously penetrate through the ground plane; and the ground plane is enclosed by the first hollowed-out portion, the second hollowed-out portion and the third hollowed-out portion into a first branch and a second branch, and the first branch and the second branch are respectively disposed on opposite sides of the first hollowed-out portion; and an edge of the first branch and an edge of the second branch are flush with edges of the second hollowed-out portion and the third hollowed-out portion, wherein a length range of the first branch and the second branch is a ratio of a wavelength at a target frequency to 4; the length of the first branch is a length from an edge that is of the first branch and that is away from the second branch to the first hollowed-out portion, the length of the second branch is a length from an edge that is of the second branch and that is away from the first branch to the first hollowed-out portion, and the target frequency is a frequency of a common mode signal attenuated by the circuit board.