Joyangnu was the upper story (Munnu) of a government office, Munsogak built by Eom Hwang, governor of Chuncheon province in 1646 (the 24th year of the King Injo's reign of the Joseon Dynasty). In 1916, an accidental fire destroyed Munsogak in 1908, but Joyangnu had been transferred to its current place, Mt. Udu, so it could avoid the fire.

This was built to control the passage of people entering and exiting the local government office. The gate has double eaves and double layers, built by the construction style of Paljakjibung (hip-and-gable roof) and Ikgong. The lower compartment was used as a passageway, while the upper compartment was for supervision and control.

The building has three compartments at the front and two compartments at the side. Four pillars are erected at the front and the rear of the building respectively and one pillar is built at the center of both sides respectively. Ten pillars in total are erected at the external side. The pillars are made of wood that rest on a square and high foundation stone used, while two squared pillars are erected on a square and low foundation stone at the left and right of the middle compartment. A flight of stairs to the second story is at the left side of the rear, and wooden boards are spaced between the wooden floors and the foundation stone at both sides of the building.

The external appearance has the same look as the common pavilions but has a low ceiling, and it does not have a hanging board bearing Chinese writings. It is due to the difference between the common pavilions and the ‘Munnu