This paper presents a systematic study on "Moving-mask UV lithography" for 3-D (three-dimensional) microstructuring of positive- and negative-tone thick photoresist and a dedicated UV lithography process simulation. As an application of the moving-mask UV lithography, we propose a novel method to fabricate embedded microfluidic structures Using SU-8. Furthermore, we propose a new practical photoresist profile simulation approach adopting the "Fast Marching Method" to consider the photoresist dissolution vector in the development process. Through a series of moving-mask UV lithography experiments, (1) the capability of the moving-mask UV lithography for 3-D microstructuring, and (2) the validity of the proposed photoresist profile simulation, were successfully confirmed.