A power consumption amount estimating apparatus for estimating a power consumption amount of a resource allocated to multiple virtual machines operating on a physical machine, the estimation being made for each virtual machine, includes a power consumption amount measuring unit configured to measure the power consumption amount of the resource; a time identifying unit configured to identify a start and an end time of a duration during which a processor is continuously allocated for one of the virtual machines; a power consumption amount obtaining unit configured to obtain the power consumption amount of the resource during the duration using the power consumption amounts at the start and end times; and a power consumption amount accumulating unit configured to accumulate multiple power consumption amounts of the resource for each virtual machine, the multiple power consumption amounts being obtained during multiple durations, respectively.