PURPOSE: To obtain the subject substance providing growth promotion and weight increase of silkworm by mixing a solution of chlorophyll in a hydrophilic organic solvent with an aqueous solution containing a water-soluble metal salt in the presence of an activator, extracting the mixture with a non-hydrophilic organic solvent and removing the solvent from the extracted solution.

CONSTITUTION: A solution of chlorophyll in a hydrophilic organic solvent (preferably an extracted solution of chlorophyll of a chlorophyll-containing plant or alga with a hydrophilic organic solvent) is mixed with an aqueous solution containing a water-soluble metal salt in the presence of an activator (preferably a phenolic acid, phenolaldehyde, a noncyclic carboxylic acid or a sulfur containing amino organic acid) to make 65-85wt.% concentration of the hydrophilic organic solvent. Then the mixture is extracted with a non- hydrophilic organic solvent and the solvent is removed from the extracted solution to give the objective substance having a visible part absorption spectrum with the maximum values at 668, 608, 533, 472 and 410nm and 504 or 495nm.