Ink bottle

The ink bottle capable of avoiding ink contamination of pen shaft during filling includes one bottle body and one bottle cap, and features that the bottle mouth is provided with one airtight flange and one elastic extending soft bag with ink inlet in the bottom and air guide port. During use, the elastic extending soft bag is soaked into ink to maintain ink level inside the bag the same as the bottle mouth and the pen is stretched into the soft bag to suck ink without ink contamination to the pen shaft. After the ink is partially used, the ink bottle may be inclined for further sucking ink until the ink is exhausted.