An automatic driving system for vehicles capable of switching between an automatic drive mode in which an own vehicle is caused to travel with automatic driving in accordance with a scheduled travel behavior along a scheduled travel route set in advance and a manual drive mode in which a driver performs driving manually, comprising: a driver's state determining unit configured to determine whether or not a state of the driver is a state of being capable of performing manual driving; a travel behavior determining unit configured to determine whether or not a travel behavior of the own vehicle during automatic driving is in a stable state of being switchable to manual driving; and a drive mode switching control unit configured to control switching from the automatic drive mode during automatic driving to the manual drive mode, characterized in that the driver's state determining unit determines the state of the driver based on an arousal state of the driver and readiness for manual driving of the driver, the travel behavior determining unit determines the travel behavior of the own vehicle based on an operational state of a steering system, an accelerating system, and/or a braking system of the own vehicle during automatic driving, the drive mode switching control unit allows switching from the automatic drive mode to the manual drive mode when the driver's state determining unit determines that the state of the driver is in a state of being capable of performing manual driving and the travel behavior determining unit determines that the travel behavior of the own vehicle is in a stable state of being switchable to manual driving, and the drive mode switching control unit provides a notification to encourage the driver to confirm readiness using a display device (11, 12) and/or a speaker of the own vehicle when the driver's state determining unit determines that the driver is in the arousal state but is not ready for manual driving, and then, the driver's state determining unit determines readiness of the driver again. a driver's state determining unit configured to determine whether or not a state of the driver is a state of being capable of performing manual driving; a travel behavior determining unit configured to determine whether or not a travel behavior of the own vehicle during automatic driving is in a stable state of being switchable to manual driving; and a drive mode switching control unit configured to control switching from the automatic drive mode during automatic driving to the manual drive mode, characterized in that the driver's state determining unit determines the state of the driver based on an arousal state of the driver and readiness for manual driving of the driver, the travel behavior determining unit determines the travel behavior of the own vehicle based on an operational state of a steering system, an accelerating system, and/or a braking system of the own vehicle during automatic driving, the drive mode switching control unit allows switching from the automatic drive mode to the manual drive mode when the driver's state determining unit determines that the state of the driver is in a state of being capable of performing manual driving and the travel behavior determining unit determines that the travel behavior of the own vehicle is in a stable state of being switchable to manual driving, and the drive mode switching control unit provides a notification to encourage the driver to confirm readiness using a display device (11, 12) and/or a speaker of the own vehicle when the driver's state determining unit determines that the driver is in the arousal state but is not ready for manual driving, and then, the driver's state determining unit determines readiness of the driver again.