To give reliability to statistical data on samples as discrete materials, a required sample-number determination device includes: a required sample number for each class acquisition unit configured to acquire a required sample number for each class Ni by the following Equation (1) based on a proportion P{circumflex over ( )}i, that is a ratio of the number of samples in each class to the number of the samples in the population; a temporary required sample number acquisition unit configured to acquire a temporary required sample number Nr, which may be a maximum value among the required sample numbers for each class Ni; and a required sample number determination unit configured to determine the temporary required sample number Nr as a true required sample number when the sample number reaches the temporary required sample number Nr or more, [ Mathematical ⁢ ⁢ 1 ] ⁢ N i = ( K P ξ i ) 2 ⁢ P ^ i ⁡ ( 1 - P ^ i ) ( 1 ) in Equation (1), ξi denotes a constant for accuracy that is set for each class, KP is a constant depending on set reliability, and i as indices denotes a class number assigned to each class.