To provide surface treatment that can reduce occurrence of defects caused by incorporation of dust. Rollers 40 are rotatably fixed to rotating shafts 72 provided to protrude from lateral protective walls 49. The lateral protective walls 49 are fixed perpendicularly to lower protective walls 47 fixed to outer walls 39. Hanging plates 64 of a hanger 50 extend through a space 43 between both lower protective walls 47 and support clips 52. A liquid 41, such as water, is filled in spaces defined by the lateral protective walls 49, the lower protective walls 47, and the outer walls 39. The liquid 41 is filled to cover about half of each rotating shaft 72. Thus, fine dust generated by a transferring mechanism is captured by the liquid 41 and prevented from drifting from the space 34 toward the substrate 54.