To obtain a strong medicinally efficacious liquid having excellent medicinal efficacy by a simple method.

This strong medicinally efficacious liquid contains an extraction solution as a main ingredient. The extraction solution is obtained by throwing sugar cane residues into a tank filled with water and immersing the thrown residues in water for prescribed days to extract the nutrients of the residues and ferment the solution, and contains useful microorganisms generated by the fermentation. The sugarcane residues comprise cut treated products obtained by cutting and crushing sugar canes or their outer skin portions peeled from the stem portions of the sugarcanes, or residue treated products obtained by crushing and squeezing the sugarcanes to squeeze out sugar contents.