In power system, spinning reserve is one of the important indicators of power system security. Regarding spinning reserve as an important factor, spinning reserve cost has been appropriated highly. This paper proposes a method for decreasing spinning reserve cost using demand respond (DR) program. The effect of DR is focused on the aspect of decrease effect of spinning reserve cost. In order to present the effect of DR, demand-price elasticity matrix is used in this paper. DR program is modeled N-period time-of-use (TOU) program, which is one of the most important economic methods in Demand-side Management (DSM). The changed load is considered two sides of DR effects, which are load curtailment and load shift. Using the changed load after DR, spinning reserve cost is recalculated. Case study is conducted on the RBTS IEEE with six buses. For the TOU program, it is assumed that parameters of time period partition consist of three time periods. Spinning reserve cost is calculated from local marginal price (LMP) and capacity price (CP) of 24 hours a day.