Abstract: A software update device is configured to update software for an in-vehicle control device mounted in a vehicle. The software update device includes an information acquisition unit, an output unit, an execution unit, a communication status acquisition unit, a correction unit, and a notification unit. The information acquisition unit is configured to acquire, from a server provided outside the vehicle, update process information related to an update of the software. The output unit is configured to output consent request information for asking a user whether to consent to the update of the software. The execution unit is configured to execute an update process for the software according to response information that is a response to the consent request information from the user. The calculation unit is configured to calculate an estimate time required for the update.