PROBLEM TO BE SOLVED: To efficiently extract effective components from humus soil material by using deep ocean water; to increase the effective components. SOLUTION: In a humic substance solution manufacturing method, the humus soil material collected from the ground is dehydrated and dried to obtain fine powder, and then the fine powder, and the deep ocean water or electrodialyzed seawater in an amount of 3-5 times the weight of the fine powder are supplied into a reaction tank to obtain suspended water. The suspended water is aged at a water temperature of 8-14°C until its pH changes from 5.5 to 3.0, and then the liquid part is separated. COPYRIGHT: (C)2006,JPO&NCIPI