Nowadays, it is hoping for the room space with the spacious comfortableness in a public building, a office building, and a housing. Though a big span slab is proposed in order to solve such a issue, there are a lot of uncertainties for the mechanical behaviors of the slab. The uncertainties are arisen from loading condition, end restraint condition, initial condition, etc. Among them, the end restraint condition is noticed, and the numerical analyses are carried so as to evaluate its effect on the behaviors or RC slab. In this article, the effect is clarified through the non-linear analytical method in which tension-softening and compressive failure can be considered.