DRIVING ASSISTANCE DEVICE AND DRIVING ASSISTANCE METHOD

A driving assistance device includes a storage medium configured to store computer-readable instructions, and a processor connected to the storage medium, in which the processor executes the computer-readable instructions to determine whether to urge a driver of a mobile object to accelerate or decelerate on the basis of a state of the mobile object, to cause a speaker to output a notification sound urging the driver of the mobile object to accelerate or decelerate on the basis of a result of the determination, to cause the speaker to output a fundamental sound when causing the speaker to output the notification sound, and then cause the speaker to output one or more additional sounds whose pitch is different from a pitch of the fundamental sound, and to cause the speaker to output the one or more additional sounds whose pitch is higher than the pitch of the fundamental sound when the driver of the mobile object is urged to accelerate.