To provide a plastic-made spacer being light in weight, being easily manufacturable, being speedily and securely connectable by simple operation and capable of corresponding to various sizes of clearance and filling a clearance between a slab and a floor board member with high precision and supporting them.

This plastic-made spacer is constituted in such a way that each of locking projections 12 is inserted into each of locking hole parts 15 in the other spacer plate 1, respectively, is rotated in the peripheral direction, and is fitted in a bayonet manner and both of these members are integrally connected to pile up and connect a plurality of spacer plates 1 mutually. A technical means is employed to form a pivotally supporting recessed part 14 at substantially the center of a bottom face side of a spacer plate body 11 and a pivotally supporting projecting part 13 at substantially the center of an upper face side of the spacer plate body 11 and let the pivotally supporting projecting part 13 in the other spacer plate 1 agree with the pivotally supporting recessed part 14 to guide trajectory of rotational operation of bayonet fitting.