The invention relates to a staircase element comprising a tubular mast erectable to a vertical position onto the floor or a corresponding surface of a stair hall, and fillable with concrete; stair step elements fastened at their first end stepwise to the mast and branching off radially from the mast; at least one tubular stringer fastened to the second end of the stair step elements, fillable with concrete and connectable with fastening members to at least one wall of the stair hall, for supporting the stair step elements at their second end and for anchoring the staircase element to a building. The invention also relates to a method for building a staircase.