An apparatus for encryption according to an embodiment of the present disclosure comprises a classifier configured to classify each data included in an original data set into one of encryption target data and non-encryption target data on the basis of at least one of determination on whether or not an operation to be applied to each data included in the original data set for an analysis of the original data set is a preset operation and determination on whether or not each data included in the original data set is sensitive information; and an encryptor configured to encrypt the encryption target data among the data included in the original data set using a homomorphic encryption algorithm.