Since James Web Space Telescope (JWST)’s launch on the 25th of December 2021, new era of astronomy has begun. We can see totally different universe ever seen before. This success would not be possible without the previous Hubble Space Telescope (HST)’s early failure. JWST is considered as a successor of HST. But it is not true. One thing in common of these two telescopes is that they are in space. They have different primary mirror, orbit, observing wavelength and scientific instruments. Probably they have the same scientific goal : revealing the origin of the Universe and life. In this article I will explain differences of JWST and HST and introduce their achievements. Furthermore I will discuss whether JWST is really a successor or substitute of HST.