1. A method for allocating time resources for a virtualization system supporting at least two operating systems (OSs), the method comprising: configuring an adjustment value for a first OS and a second OS, and configuring a threshold value for time resource adjustment for each of the first OS and the second OS, the threshold value including an upper limit and a lower limit of the time resources; allocating time resources to the operating systems; calculating, when at least one of the operating systems is running, workloads for each operating system; adjusting time resources allocated to the first OS based on the calculated workloads and the adjustment value; determining, if the time resources of the first OS are decreased by the adjustment value, whether the adjusted time resources are less than the lower limit of the time resources of the first OS; allocating, if the adjusted time resources of the first OS are less than the lower limit of the time resources of the first OS, the lower limit of time resources of the first OS as a new time resources of the first OS; determining, if the time resources of the first OS are increased by the adjustment value, whether the adjusted time resources of the first OS are greater than the upper limit of the time resources of the first OS; determining, if the adjusted time resources of the first OS are greater than the upper limit of the time resources of the first OS, whether a value of the upper limit of the time resources of the second OS minus current time resources of the second OS is greater than the adjustment value; and allocating, if the value is greater than the adjustment value, the adjusted time resources of the first OS which is greater than the upper limit of time resources of the first OS as a new time resources of the first OS and decreasing the upper limit of time resources of the second OS by the adjustment value.