There are several different opinions on this question.
- Strict interpretation of "authorship": An "author" of a scientific publication is somebody who contributed directly to the research as well as to the writing of the publication and can be held responsible for any mistakes in the publication. Several style guides for scientific publications require this interpretation when determining the authors list. According to that interpretation, you would not add him as an author.
- Loose interpretation of "authorship": An "author" is a major contributor at least to the research itself. According to this interpretation, you could add your advisor as an author.
- "My chances of acceptance are better this way": some people ignore morality and simply put their advisor on their paper as an author because their advisor may be a repected scientist in this field of research, and the mere presence of his name on the publication may improve the chances of being accepted.
- "My reputation will improve more this way": On the other hand, some people may choose to explicitly omit their advisors' names from their publications for thinking that an accepted publication with them as the only author will improve their reputation more than a shared publication where it is unclear which author did what part of the job
- "He demands it": Some advisors are the bosses of their PhD students and simply require their student to list them as authors, in order to improve their own publication list.
Personally, I'd got with the honest way, Number 1, and optionally thank your advisor in an "Acknowledgement" section (usually the final section of the paper, right before the bibliography). A typical acknowledgement reads
"The authors wish to express their gratitude towards [person] for [deed]"