A chemical supply system comprises, as principal elements, a chemical
storage tank in which a liquid chemical for cleaning is stored in the
state of its formulated concentrate, a chemical supply apparatus
connected to the chemical storage tank for positively performing chemical
supply, a piping system connected to the chemical supply apparatus to
form a supply flow passage that is a passage for ultrapure water which
the liquid chemical is to be mixed with, a pair of discharge nozzles
disposed at end portions of the piping system so as to oppose surfaces of
a wafer set in a cleaning chamber to supply a cleaning liquid onto the
surfaces. Thereby, remarkable miniaturization/simplification of a
cleaning liquid supply system including chemical tanks is intended, it is
made possible easily and rapidly to compound and supply a cleaning liquid
at an accurate chemical concentration, and particles or the like being
generated and mixing in a cleaning liquid, are suppressed to the
extremity.