Three-dimensional current structure in the ionsphere (90--400 km) is calculated for (1,--2) tidal winds, assuming that the parallel conductivity (&sgr;0) is infinite and therefore that the electrostatic potential is constant along magnetic field line. Calculated structure of height-integrated currents is essentially the same as the observed Sq current system. It is also shown that a meridional current system alwasy exists in the equatorial region and that the east-west component of currents could be reversed only near the equator. Though electric currents flow mainly in the E region, currents in the F region contribute a little, especially to poleward currents at middle and high latitudes.