A processing time estimation method for estimating a processing time of each of a plurality of jobs, the processing time estimation method including determining, executed by a computer, whether the each job has a preceding job thereof on the basis of previous execution data including previous information of a plurality of previous start times and previous finish times of respective jobs of the plurality of jobs, the preceding job of the each job being included in the plurality of jobs and at least having the previous finish time earlier than the previous finish time of the each job.