To provide a method for producing a humic acid liquid by which the decomposition of a useful material originally involved by the humic acid can be prevented.

Water and an alkali aqueous solution are added to peat, and the resultant mixture is stirred and separated into liquid and a precipitate. The mixing ratio of the peat, water and the aqueous alkali solution are regulated so that the amount of the peat and the amount of the alkali aqueous solution may be 10-30 pts. wt. and 1-3 pts. wt. respectively, based on 100 pts. wt. water. Preferably, the alkali aqueous solution is the solution of one of sodium hydroxide, potassium hydroxide, slaked lime and ammonia, especially, potassium hydroxide. The peat is preferably Songhua river coal (R) produced in the northeast district of China.