A method is provided in which a correlation is made between a parameter indicating modification of a sampled malt in a germination process in which barley is germinated, and an ESR signal intensity of the sampled malt. The parameter is determined, in advance, by general analytical methods including chemical analytical methods. The ESR signal intensity is determined by measuring a peak height of spectrum of the sampled malt at a g value at which an unpaired electron derived from a carbon radical is resonant. The ESR signal intensity is a ratio of the measured peak height of spectrum to a peak height of spectrum of a reference, per a unit weight of the sampled malt. The modification state of the sampled malt can be evaluated based on the ESR signal intensity determined by electron spin resonance spectrometry. Kohlbach index, Hartong index at 45 C., diastatic power, -glucan content, viscosity, and friability may be used as the parameter.