To faithfully represent a shape pattern by consisting a concrete hardening delaying agent layer of a sheet for exposing aggregate by washing of the fine porous body in which a water insoluble resin or slightly water soluble resin and the concrete hardening delaying agent are mixed.

A sheet 1 in which a concrete hardening delaying agent layer 2 formed of the fine porous body consisting of a composition where a water insoluble resin or slightly water soluble resin and a concrete hardening delaying agent are mixed is attached to a mold 10, a concrete material 5 is poured therein, and the mold 10 and the sheet 1 are separated after hardening. A part in contact with the delaying agent layer 2 on the surface of a concrete product 6 becomes a non-hardened surface layer 4, the water content in the concrete material 5 is penetrated from fine pores in the delaying agent layer 2, the delaying agent is slightly solved, and gradually diffused into the concrete material 5 along the insoluble resin which is hardened in the fine porous manner, and the depth and the range of the non-hardened surface layer 4 become uniform. When the non-hardened surface layer 4 is washed by spraying the high pressure water against the concrete product 6, the contour of the pattern of the exposed aggregate faithfully represents the shape pattern.