This thesis presents accurate analyses of the spin-orbit angle for many remarkable transiting exoplanetary systems, including the first measurement of the Rossiter-McLaughlin effect for a multiple transiting system. Â The author presents the observational methods needed to probe the spin-orbit angle, the relation between the stellar spin axis and planetary orbital axis. Measurements of the spin-orbit angle provide us a unique and valuable opportunity to understand the origin of close-in giant exoplanets, called "hot Jupiters". Â The first method introduced involves observations of the Rossiter-McLaughlin effect (RM effect). The author points out the issues with the previous theoretical modeling of the RM effect and derives a new and improved theory. Applications of the new theory to observational data are also presented for a number of remarkable systems, and the author shows that the new theory minimizes the systematic errors by applying it to the observational data. Â The author also describes another method for constraining the spin-orbit angle: by combining the measurements of stellar flux variations due to dark spots on the stellar surface, with the projected stellar rotational velocity measured via spectroscopy, the spin-orbit angles "along the line-of-sight" are constrained for the transiting exoplanetary systems reported by the Kepler space telescope.
