A balance-unbalance conversion apparatus, comprising: an insulation substrate; a first microstrip, wherein the first microstrip comprises a first balance signal connecting section, a first impedance matching section, and an unbalance signal connecting section that are sequentially connected, the first balance signal connecting section is configured to transmit a first component of a balance signal, and the unbalance signal connecting section is configured to transmit an unbalance signal; a second microstrip, wherein the second microstrip comprises a second balance signal connecting section, a second impedance matching section, and a ground section that are sequentially connected, the second balance signal connecting section is configured to transmit a second component of the balance signal, and the ground section is configured to connect to a ground signal; and a conductive ground, wherein the conductive ground is a reference ground of the first balance signal connecting section and the second balance signal connecting section, wherein the first microstrip, the second microstrip, and the conductive ground are all disposed on the insulation substrate, the first balance signal connecting section and the second balance signal connecting section are located on a same plane of the insulation substrate, the first impedance matching section of the first microstrip and the second impedance matching section of the second microstrip are separated by the insulation substrate; and a cross-sectional area of at least a part of the first microstrip and/or at least a part of the second microstrip is gradient; and wherein the first balance signal connecting section comprises a first parallel section and a first tilt section, the first parallel section is configured to transmit the first component of the balance signal, one end of the first tilt section is connected to the first parallel section, and the other end is connected to the first impedance matching section; the second balance signal connecting section comprises a second parallel section and a second tilt section, the second parallel section is parallel to the first parallel section, the second parallel section is configured to transmit the second component of the balance signal, one end of the second tilt section is connected to the second parallel section, and the other end is connected to the second impedance matching section; and the conductive ground comprises a first reference ground and a second reference ground, the first reference ground is a reference ground of the first parallel section and the second parallel section, and the second reference ground is a reference ground of the first tilt section and the second tilt section. an insulation substrate; a first microstrip, wherein the first microstrip comprises a first balance signal connecting section, a first impedance matching section, and an unbalance signal connecting section that are sequentially connected, the first balance signal connecting section is configured to transmit a first component of a balance signal, and the unbalance signal connecting section is configured to transmit an unbalance signal; a second microstrip, wherein the second microstrip comprises a second balance signal connecting section, a second impedance matching section, and a ground section that are sequentially connected, the second balance signal connecting section is configured to transmit a second component of the balance signal, and the ground section is configured to connect to a ground signal; and a conductive ground, wherein the conductive ground is a reference ground of the first balance signal connecting section and the second balance signal connecting section, wherein the first microstrip, the second microstrip, and the conductive ground are all disposed on the insulation substrate, the first balance signal connecting section and the second balance signal connecting section are located on a same plane of the insulation substrate, the first impedance matching section of the first microstrip and the second impedance matching section of the second microstrip are separated by the insulation substrate; and a cross-sectional area of at least a part of the first microstrip and/or at least a part of the second microstrip is gradient; and wherein the first balance signal connecting section comprises a first parallel section and a first tilt section, the first parallel section is configured to transmit the first component of the balance signal, one end of the first tilt section is connected to the first parallel section, and the other end is connected to the first impedance matching section; the second balance signal connecting section comprises a second parallel section and a second tilt section, the second parallel section is parallel to the first parallel section, the second parallel section is configured to transmit the second component of the balance signal, one end of the second tilt section is connected to the second parallel section, and the other end is connected to the second impedance matching section; and the conductive ground comprises a first reference ground and a second reference ground, the first reference ground is a reference ground of the first parallel section and the second parallel section, and the second reference ground is a reference ground of the first tilt section and the second tilt section.