Since the energy scale of inflation can be still as high as 10^14GeV, inflation can provide a natural laboratory to test high energy physics. In this talk, I will discuss possible imprints of string theory in inflationary universe and their detectabilities in various cosmological observations. First, I will discuss imprints of higher spin particles, which can appear from compactification in string theory, supplying a couple of arguments which were not discussed in Arkani-Hamed & Maldacena(15) and Schmidt et al. (15, 16), but are needed to complete the analysis. Second, I will discuss cosmological consequences of stringy axions with interference, which can appear in supergravity setup.