A distributed processing system 100 is used in which a plurality of machines including a virtual machine constructed by cloud computing perform distributed execution of a task. Machines 2 to 9 each include: a communication unit 302 that acquires environment information relating to the environment of another machine other than the own machine; an information acquisition unit 303 that acquires environment information relating to the environment of the own machine; a risk calculation unit 305 that calculates a risk for the case where the own machine executes the task based on the acquired environment information; a risk determination unit 306 that determines whether or not the calculated risk is equal to or higher than a predetermined threshold; and an execution control unit 307 that stops execution of the task on the own machine when the risk determination unit 306 determines that the risk is equal to or higher than the predetermined threshold.