A time-series data management method for generating a histogram from time-series data using a computer provided with a processor and a storage device, the computer storing the time-series data including a time of day and a value in the storage device, storing section information including a start time, an end time, and an identifier of the time-series data in the storage device, generating the histogram from the time-series data corresponding to the section information and storing the generated histogram in the storage device, accepting a section to be searched and selecting the histogram associated with the section to be searched, and combining the selected histograms and generating a histogram for the section to be searched