The present paper deals with the two-dimensional viscous flow around a circular cylinder moving at low speeds along the central plane parallel to two parallel side planes. It is semi-analytically solved by applying the collocation method for the stream function. The present results for velocity, pressure and viscous stress agree well with other numerical results. The pressure drag and the friction drag on a cylinder are obtained from the pressure distribution and the viscous stress distribution at the surface of a circular cylinder, respectively. It is shown that the pressure drag is larger than the friction drag and the ratio of the former to the latter decreases with increase of the distance between the two parallel side planes. An empirical formula for the drag which fits the present results is obtained by modifying Faxen's analytical formula. The new formula covers a wider range of the distance between the two side planes than Faxen's one.