A readily attaching-detaching structure of a front loader that can make the attaching and detaching work to a vehicle body easier, a front loader, and a work vehicle. The attaching-detaching structure of a front loader is provided with a first retained member that is on either a main frame on a vehicle body or a sub-frame that supports a boom; a second retained member on the other of the main frame or the sub-frame; a first retaining member that retains the first retained member and is on the side opposite of the first retained member; a second retaining member that retains the second retained member and is on the side opposite to the second retained member; a first guiding member that guides the first retained member to the first retaining member when the sub-frame is mounted on the main frame; and a second guiding member that guides the second retained member to the second retaining member when the sub-frame is mounted on the main frame.