To provide a strength increasing method for a high-strength concrete structure, by which the situation, in which a strength distribution in the same member is brought to the state of uneven quality, can be avoided and the reduction of the quantity of heat effective for a strength manifestation can be inhibited.

In the strength increasing method for the high-strength concrete structure 3 applied even under weather conditions, in which a daily mean air temperature exceeds 4°C, the strength increasing method contains a placing process, in which high-strength concrete 3a is placed to forms 1, and a curing process carried out while inhibiting a heat dissipation by heat-insulating a region brought into contact with the outside air through the forms 1 or through no form 1 as the peripheral region of the placed high-strength concrete 3a.