This study concerns surface wave attenuation by viscosity, in particular, the effect of viscosity on the interior motion of the fluid. The standing wave formed near an obstacle in a horizontal channel is chosen as the subject of this analysis because gravitational and surface tension waves appear separately before and behind the obstacle, and, hence, the effect of viscosity on two typical kinds of waves can be analysed. The linearized differential equation for the stream function is solved analytically to obtain the waveform. The calculated attenuation rate of wave amplitude does not agree well with that of Stokes' approximate estimation based on the irrotational solution. This shows that the Stokes' estimation is not sufficient and the exact analysis as presented here is necessary when the Reynolds number is relatively low as Re≤1 000. As an application of this analysis, the wave form is calculated for the standing wave formed by an obstacle in falling liquid film flow.