To provide a balanced door and a movement auxiliary device for a balanced door capable of reducing burden when a door body is opened and closed.

A balanced door 10 includes: a frame body 11 having an opening 14; a door body 15 having a first door body 16 swingably connected to the frame body 11 around a rotary shaft 16A and a second door body 17 swingably connected to the first door body 16 around a rotary shaft 17A, so as to block the opening 14; a striker 20 projecting toward a horizontal frame 13; and a guide part 30 guiding the striker 20 along the horizontal frame 13. The guide part 30 includes: a closing movement auxiliary mechanism 50B capturing the striker 20 when the door body 15 closes and guiding the captured striker 20 to a closed position; and an opening movement auxiliary mechanism 50A capturing the striker 20 when the door body 15 opens and guiding the captured striker 20 to an opened position.