At least one of the partition walls (4-10) inside the office has a section (41, 51, 61, 91, 101) which is pivotally connected to the office base structure (1) or one of the boxes (2, 3) so that it can be pivoted about a vertical axis close to the central length axis for the base structure or about a vertical axis close to one of the box length side walls (21, 31) so that it extends parallel to the box latter, allowing the box to be folded away into its retracted position. An orthogonal parallelepiped base structure is mounted on a chassis with wheels and has an opening in each of its two opposing side walls for locating an orthogonal parallelepiped box which is open on the side facing the base structure. Each box can be moved in a linear manner between a retracted position in which the box side wall is next to the base structure side wall and an extended position in which the box side wall is located beyond the base structure side wall. The partition walls extend in the office cross- direction.