The transit observations have revealed interesting features of the sizes, orbital periods, and these relations of the observed planets. We have investigated the size evolution of planets via both giant impacts and photoevaporation. The size of a planet is given by the summation of its core and envelope sizes and calculated by analytical models. We perform N-body simulations to track the size evolution of planets in giant impacts and consider the shock-wave-induced envelope stripping in each giant impact. We find that inner planets sometimes lose their whole envelopes via giant impacts, while outer planets can keep their initial envelopes because they do not experience giant impacts. We perform photoevaporation simulations afterward. Our results suggest that the period-radius distribution of the observed planets would be reproduced when the initial distributions of the core masses have wide ranges in power-law distributions. We find that the sizes of the final adjacent planetary pairs become similar since they have similar mass and envelope mass fractions, which originated from the similar initial core mass and envelope mass fractions of protoplanets.