We propose a simple but effective mechanism to realize an inflationary early universe consistent with the observed WMAP, Planck and/or BICEP2 data which would be incorporated in numerous particle physics models constructed in a (effective) five-dimensional spacetime. In our scenario, the inflaton field is identified with one of the moduli appearing when the fifth direction is compactified, and a successful cosmological inflation without a so-called $\eta$ problem can be achieved by a very simple moduli stabilization potential without breaking the supersymmetry at the vacuum. We also discuss the related particle cosmology during and (just) after the inflation, such as a (no) cosmological moduli problem.