Door opening and closing device

A door opening and closing device, comprising:

• a motor configured to output driving force that causes a back door of a vehicle to be opened or closed;
• and
• a controller configured to control the motor, wherein
• the controller executes, according to an automatic opening and closing command, automatic opening and closing control for automatically opening or closing the back door from a first position to a second position by the motor, the first position being a door position at which the automatic opening and closing control is started, the second position being a door position at which the automatic opening and closing control ends,
• when the controller, during a movement of the back door from the first position to the second position under the automatic opening and closing control, detects a stop command causing the back door to be stopped at a third position between the first position and the second position, the controller decreases target velocity of the back door at a constant deceleration from a time of a detection of the stop command until the back door stops at the third position,
• the controller, according to the automatic opening and closing command, further controls the motor to decrease the target velocity of the back door at a predetermined deceleration from a fourth position to the second position,
• the fourth position is disposed between the first position and the second position, and
• a deceleration rate of the constant deceleration is higher than a deceleration rate of the predetermined deceleration.