A medical data processing device classifies a tumor type by using a first numerical sequence indicating a time series variation of a feature value of a tumor region including a tumor. The first numerical sequence is obtained from echo signals obtained from a living organism after administration of a contrast agent. The medical data processing device includes a first classifier that extracts, from the first numerical sequence, a first numerical sequence portion of a classification interval having a predefined time period shorter than the entire time of the first numerical sequence and classifies the tumor type by using the first numerical sequence portion.
