A data generation device includes a large-scale data acquisition unit that obtains large-scale data that is large-scale learning data used in learning of a first determination model for determining a machining state of a workpiece machined by a first machine tool; an adaptive data acquisition unit that obtains adaptive data for use in generation of learning data for use in learning of a second determination model for determining a machining state of a workpiece machined by a second machine tool; and a learning data generation unit that converts the large-scale data based on the adaptive data to generate adapted large-scale data for use in learning of the second determination model.