For the purpose of providing a staircase which has a lightweight structure, high efficiency in manufacturing and constructing, and creates a sense of lightness in weight, a staircase is composed with a pair of right and left stringers made of truss structural members (10), and treads (12). The truss structural members (10) are composed of the upper chord members (1) and the lower chord members (2) inclined with the slope of the staircase, and a plurality of lattice members (4) for linking the upper chord members (1) and the lower chord members (2), and between the truss structural members (10) are fixed a plurality of linking members (11) which are laid horizontally at each riser height and on which the treads (12) are fixedly supported.