The influence of a quartz side wall on plasma production was studied in a large-area surface wave plasma source. An enhanced plasma production was observed in the vicinity of the quartz side wall and is explained by the propagation of the surface wave coupled from the bottom quartz plate to the quartz side wall. This was confirmed by measuring the electromagnetic field intensity and the wavelength of the surface wave propagating along the side wall. Additionally, the plasma density was obtained by two different methods, that is, calculation using the dispersion relation and measurement using a Langmuir probe. It was found that the surface wave propagates along the quartz side wall in the direction perpendicular to the slot antenna axis, resulting in plasma production. As a consequence, the radial plasma density becomes more uniform in the region with the quartz side wall than in the region with a metal side wall.