Periphery monitoring device

A periphery monitoring device comprising:

• an image acquisition unit acquiring an image obtained from an imaging unit imaging a situation surrounding a towing vehicle to which a towed vehicle is connectable;
• a projection plane acquisition unit acquiring a three-dimensional virtual projection plane onto which the image can be projected, the virtual projection plane being provided with a side plane rising in a height direction from a grounding surface of the towing vehicle;
• a projection processing unit projecting the image onto the virtual projection plane;
• a viewpoint setting unit setting a viewpoint position and a gazing point position with respect to the virtual projection plane;
• an image display unit causing a display device to display an image obtained by viewing the gazing point position from the viewpoint position with respect to the virtual projection plane;
• and
• a determination unit determining whether or not the towed vehicle is connected to the towing vehicle,
• wherein the periphery monitoring device changes at least one of a shape of the virtual projection plane, the viewpoint position, the gazing point position, and a viewpoint moving speed at which the viewpoint position is moved, in accordance with a result of the determination of the determination unit.