It is an object of the present invention to provide a method for producing
gold colloid having a targeted particle size, a sharp particle size
distribution and a uniform and perfect spherical shape. The present
invention relates to a method for producing gold colloid including a
nucleation step of forming nuclear colloidal particles by adding a first
reducing agent to a first gold salt solution; and a growth step of
growing nuclear colloid by adding a second gold salt and a second
reducing agent to the solution of the nuclear colloidal particles,
characterized in that the growth step is performed at least once; a
citrate is used as the first reducing agent and an ascorbate is used as
the second reducing agent; and the addition of the ascorbate in the
growth step is performed simultaneously with addition of the second gold
salt. According to the method for producing gold colloid of the present
invention, gold colloid having a sharp particle size distribution and a
uniform and perfect spherical shape can be obtained.