A connector having a counter connector terminal housing portion in which part of a counter connector terminal is to be inserted, the connector comprising: a connector terminal having a connection surface in a flat shape that faces the counter connector terminal when inserted in the counter connector terminal housing portion; a plurality of balls in a spherical shape being disposed on the connection surface, at least surfaces of the plurality of balls having electrical conductivity; a ball retention member rotatably retaining the plurality of balls in such a manner part of the surfaces of the plurality of balls contacts the connection surface and another part of the surfaces of the plurality of balls that faces opposite from the connection surface protrudes; a ball guide portion fixed to the connector terminal and retaining the ball retention member such that the ball retention member is movable in a two-dimensional manner along the connection surface; and a terminal spring pressing the counter connector terminal when inserted in the counter connector terminal housing portion or the connection surface of the connector terminal in a direction closer together, wherein the ball guide portion includes a plurality of return springs that are disposed to surround the ball retention member along the connection surface and act to return the ball retention member to an initial position on the connection surface, the ball retention member 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 the ball retention member returns to the initial position due to action of the plurality of return springs when the counter connector terminal is pulled out from the counter connector terminal housing portion, and the counter connector terminal when inserted in the counter connector terminal housing portion is pressed against the connection surface by the terminal spring, contacts protruding parts of the surfaces of the plurality of balls retained in the ball retention member, and is electrically connected to the connector terminal via the plurality of balls. a connector terminal having a connection surface in a flat shape that faces the counter connector terminal when inserted in the counter connector terminal housing portion; a plurality of balls in a spherical shape being disposed on the connection surface, at least surfaces of the plurality of balls having electrical conductivity; a ball retention member rotatably retaining the plurality of balls in such a manner part of the surfaces of the plurality of balls contacts the connection surface and another part of the surfaces of the plurality of balls that faces opposite from the connection surface protrudes; a ball guide portion fixed to the connector terminal and retaining the ball retention member such that the ball retention member is movable in a two-dimensional manner along the connection surface; and a terminal spring pressing the counter connector terminal when inserted in the counter connector terminal housing portion or the connection surface of the connector terminal in a direction closer together, wherein the ball guide portion includes a plurality of return springs that are disposed to surround the ball retention member along the connection surface and act to return the ball retention member to an initial position on the connection surface, the ball retention member 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 the ball retention member returns to the initial position due to action of the plurality of return springs when the counter connector terminal is pulled out from the counter connector terminal housing portion, and the counter connector terminal when inserted in the counter connector terminal housing portion is pressed against the connection surface by the terminal spring, contacts protruding parts of the surfaces of the plurality of balls retained in the ball retention member, and is electrically connected to the connector terminal via the plurality of balls.