A software updating device for executing processing for updating software causing equipment mounted on a vehicle to operate, the vehicle including a power train, wherein the software updating device includes: a detection unit that detects a driving force output state of the power train of the vehicle, and a controller that acquires the software and controls the equipment by applying the software to the equipment, the controller including: a first storage unit for storing a first software, and a second storage unit for storing a second software; wherein, when the first software stored in the first storage unit is being applied to the equipment to be controlled, the controller acquires and stores the second software in the second storage unit, the equipment not being stopped during the acquisition and storage of the second software; wherein, when the detection unit detects a state where no driving force is output by the power train of the vehicle, the controller executes processing for updating the software by changing software to be applied to the equipment from the first software to the second software in the state where no driving force is output by the power train of the vehicle; wherein the controller prohibits outputting the driving force by the power train of the vehicle while the processing for updating the software is being executed; and wherein the state where no driving force is output by the power train is the off state of the engine where the engine speed is 0, or the neutral or parking state of the transmission. wherein the software updating device includes: a detection unit that detects a driving force output state of the power train of the vehicle, and a controller that acquires the software and controls the equipment by applying the software to the equipment, the controller including: a first storage unit for storing a first software, and a second storage unit for storing a second software; a detection unit that detects a driving force output state of the power train of the vehicle, and a controller that acquires the software and controls the equipment by applying the software to the equipment, the controller including: a first storage unit for storing a first software, and a second storage unit for storing a second software; wherein, when the first software stored in the first storage unit is being applied to the equipment to be controlled, the controller acquires and stores the second software in the second storage unit, the equipment not being stopped during the acquisition and storage of the second software; wherein, when the detection unit detects a state where no driving force is output by the power train of the vehicle, the controller executes processing for updating the software by changing software to be applied to the equipment from the first software to the second software in the state where no driving force is output by the power train of the vehicle; wherein the controller prohibits outputting the driving force by the power train of the vehicle while the processing for updating the software is being executed; and wherein the state where no driving force is output by the power train is the off state of the engine where the engine speed is 0, or the neutral or parking state of the transmission.