Bacterial swimming mediated by flagellar rotation is one of the most ubiquitous forms of cellular locomotion, and it plays a significant role in many biological processes. A typical swimming path of flagellated bacteria looks like a random walk with no purpose, but the random movement becomes modified as environmental conditions change. The modified random movement is particularly characterized by their motility pattern or a combination of their swimming modes. Further, such individual swimming patterns describe the collective behavior of a population of bacteria. This talk presents several distinct motility patterns exhibited by bacterial species. We also discuss how to analyze the collective behavior of bacteria from the individual swimming pattern, particularly by using an example of E. coli’s swimming behavior in response to chemical signals.