In order to apply antibiotics as agricultural chemicals, the establishment of the testing methods for their antifungal activities in the laboratory seems to be most important. In this paper, three methods of the agar streak dilution method, the paper disk diffusion methods and the spore germination test on the slide glass were compared. As the test organisms, Piricularia Oryzae, Ophiobolus Miyabeanus, Macrosporium bataticola, Alternaria Kikuchiana, Sclerotinia Mali, Penicillium Q 176 and Aspergillus niger were used. As the test antibiotics, Antipiriculin A (Antimycin A), Aureothricin, Eurocidin and Trichomycin were used, and phenyl mercuric acetate was employed as the control. A definite quantitative relation between the antifungal activities obtained by the three testing methods could not be found. The results obtained by three testing methods gave the different antifungal activities by each organism, and the relation between three methods was different by each antibiotic. But, generally, the concentration required to decide the antifungal activity of each antibiotic was lowest in the agar streak dilution method, and the next in the spore germination test, and highest in the paper disk diffusion method. Among these antibiotics there was no one which showed higher activity than phenyl mercuric acetate, but Aureothricin and Trichomycin were better than the others.