In this paper we outline the design of in-pipe inspection vehicle for pipes with ø25, ø50, ø150mm in diameter, ""Theseuse"" series. First we introduce the concept ""Whole Stem Drive"". This concept is very effective to allow an in-pipe vehicle to travel long distance in the pipeline. Based on this concept, we have made three in-pipe vehicles, Theseus-I∼III. First, for the pipe with 50mm in diameter, we propose two mechanisms, in-pipe vehicle with spiral motion (Theseus-I) and in-pipe vehicle for the practical gas pipe (Theseus-II). Next, for the pipe with 150mm in diameter, we propose the in-pipe vehicle based on the idea of Control Configured Vehicle (CCV), Theseus-III. Last, for the pipe with 25mm in diameter, we propose the in-pipe vehicle, which has an actuator outside of the pipe (Theseus-IV).