A connector having a counter connector terminal housing portion which is configured for a part of a counter connector terminal being inserted into it, the connector comprising: a connector terminal having a connection surface in a flat shape that faces the counter connector terminal when it is inserted in the counter connector terminal housing portion; at least one ball in a spherical shape that is disposed on the connection surface, at least a surface of the ball having electrical conductivity; a ball retaining portion (15A, 24C) retaining the ball such that the ball is rotatable in a state where a part of the surface of the ball contacts the connection surface and another part of the surface of the ball facing opposite from the connection surface protrudes; a ball guiding portion (14, 24) fixed to the connector terminal and holding the ball retaining portion such that the ball retaining portion is movable in a two-dimensional manner along the connection surface; and a terminal spring configured to press the counter connector terminal inserted in the counter connector terminal housing portion or the connection surface of the connector terminal in such a direction that the counter connector terminal and the connection surface approach each other, wherein, when the counter connector terminal is inserted in the counter connector terminal housing portion, the counter connector terminal is pressed against the connection surface by the terminal spring, contacts a protruding part of the surface of the ball retained by the ball retaining portion, and is electrically connected to the connector terminal via the ball, characterized in that the ball guiding portion (14, 24) includes a fixed portion (14A, 24A) fixed to the connector terminal and a return spring (14B, 24B) connected to the fixed portion and returning the ball retaining portion to an initial position on the connection surface, wherein the ball retaining portion (15A, 24C) moves in a two dimensional manner along the connection surface in accordance with movement of the counter connector terminal when the counter connector terminal is inserted into the counter connector terminal housing portion and in a connected state between the counter connector terminal and the connector terminal, and returns to the initial position due to action of the return spring when the counter connector terminal is pulled out from the counter connector terminal housing portion, and wherein the return spring (14B, 24B) extends along the connection surface and is formed from a band-like member being bent. a connector terminal having a connection surface in a flat shape that faces the counter connector terminal when it is inserted in the counter connector terminal housing portion; at least one ball in a spherical shape that is disposed on the connection surface, at least a surface of the ball having electrical conductivity; a ball retaining portion (15A, 24C) retaining the ball such that the ball is rotatable in a state where a part of the surface of the ball contacts the connection surface and another part of the surface of the ball facing opposite from the connection surface protrudes; a ball guiding portion (14, 24) fixed to the connector terminal and holding the ball retaining portion such that the ball retaining portion is movable in a two-dimensional manner along the connection surface; and a terminal spring configured to press the counter connector terminal inserted in the counter connector terminal housing portion or the connection surface of the connector terminal in such a direction that the counter connector terminal and the connection surface approach each other, wherein, when the counter connector terminal is inserted in the counter connector terminal housing portion, the counter connector terminal is pressed against the connection surface by the terminal spring, contacts a protruding part of the surface of the ball retained by the ball retaining portion, and is electrically connected to the connector terminal via the ball, characterized in that the ball guiding portion (14, 24) includes a fixed portion (14A, 24A) fixed to the connector terminal and a return spring (14B, 24B) connected to the fixed portion and returning the ball retaining portion to an initial position on the connection surface, wherein the ball retaining portion (15A, 24C) moves in a two dimensional manner along the connection surface in accordance with movement of the counter connector terminal when the counter connector terminal is inserted into the counter connector terminal housing portion and in a connected state between the counter connector terminal and the connector terminal, and returns to the initial position due to action of the return spring when the counter connector terminal is pulled out from the counter connector terminal housing portion, and wherein the return spring (14B, 24B) extends along the connection surface and is formed from a band-like member being bent.