An earphone adapted to fit into a pinna of a user, the earphone comprising: a main body unit having: a base, a top panel and a cap; the base having: a bottom formed on the opposite side of the top panel; a peripheral wall extending between the top panel and the bottom, one edge portion of the peripheral wall having an arc shape corresponding to the shape of an inner wall of the antihelix (Eb) of the user; a supporter having a cover portion for covering part of the top panel of the main body unit, wherein the top panel is configured to close a side opposite to the bottom of the base, which is released; and a cap configured to engage with an opening (12b1) of the top panel and to form a sound tube portion extending outward from the main body unit, wherein the supporter is configured to be attachable and detachable to/from the main body unit, and adapted for covering at least a protruding portion of the top panel, which is adjacent to the one edge portion of the main body unit, wherein the supporter is formed with flexibility materials, wherein the supporter includes a protruding portion that has an arc shape matched to the arc shape of the one edge portion and that protrudes from the top panel in accordance with the height of the antihelix (Eb) of the pinna, wherein the cap is formed in a funnel shape to have an increasing diameter from the sound tube portion toward the opening (12b1) of the top panel, the earphone further comprising: an earpiece attached to the sound tube portion, wherein the earpiece is configured such that when the earpiece is inserted inside the ear canal (Ea) of the user or is placed to an entrance edge portion of the ear canal (Ea), the one edge portion of the main body unit is coming into contact with the arc range in the peripheral direction in the inner wall of the antihelix (Eb), and the supporter contacts the concha auriculae (Ec) of the pinna so as to substantially adhere. a main body unit having: a base, a top panel and a cap; the base having: a bottom formed on the opposite side of the top panel; a peripheral wall extending between the top panel and the bottom, one edge portion of the peripheral wall having an arc shape corresponding to the shape of an inner wall of the antihelix (Eb) of the user; a bottom formed on the opposite side of the top panel; a peripheral wall extending between the top panel and the bottom, one edge portion of the peripheral wall having an arc shape corresponding to the shape of an inner wall of the antihelix (Eb) of the user; a supporter having a cover portion for covering part of the top panel of the main body unit, wherein the top panel is configured to close a side opposite to the bottom of the base, which is released; and a cap configured to engage with an opening (12b1) of the top panel and to form a sound tube portion extending outward from the main body unit, wherein the supporter is configured to be attachable and detachable to/from the main body unit, and adapted for covering at least a protruding portion of the top panel, which is adjacent to the one edge portion of the main body unit, wherein the supporter is formed with flexibility materials, wherein the supporter includes a protruding portion that has an arc shape matched to the arc shape of the one edge portion and that protrudes from the top panel in accordance with the height of the antihelix (Eb) of the pinna, wherein the cap is formed in a funnel shape to have an increasing diameter from the sound tube portion toward the opening (12b1) of the top panel, the earphone further comprising: an earpiece attached to the sound tube portion, wherein the earpiece is configured such that when the earpiece is inserted inside the ear canal (Ea) of the user or is placed to an entrance edge portion of the ear canal (Ea), the one edge portion of the main body unit is coming into contact with the arc range in the peripheral direction in the inner wall of the antihelix (Eb), and the supporter contacts the concha auriculae (Ec) of the pinna so as to substantially adhere. an earpiece attached to the sound tube portion, wherein the earpiece is configured such that when the earpiece is inserted inside the ear canal (Ea) of the user or is placed to an entrance edge portion of the ear canal (Ea), the one edge portion of the main body unit is coming into contact with the arc range in the peripheral direction in the inner wall of the antihelix (Eb), and the supporter contacts the concha auriculae (Ec) of the pinna so as to substantially adhere.