Before attempting to answer that question, we must first admit that it is an awesome paradigm of semantic ambiguity. For by it we could be asking several things. Does the thing called 'science fiction' exist? Does a book called 'Science' belong in the fiction section of a bookstore? Is all of the knowledge produced by scientists false? Are there actually not scientists at all? Is the history of science nothing more than a tremendously large multi-book novel written by various authors?
Actually, none of those interpretations capture the intended meaning. What the question is meant to ask is this: is the activity of scientists and/or the knowledge produced by that activity a work of fiction (viz. a product of creativity and imagination)?
Note that when I say 'imagination' I do not mean it in the sense of imaginary-as-in-not-real, I mean it in the sense of Einstein using his imagination to devise his thought experiments, or of Schrödinger imagining a cat in a radioactive box.
Which brings us to an additional clarification: fiction (although defined as a product of the creative imagination) is no more assuredly false than nonfiction (also a product of the creative imagination I would argue) is assuredly true. Put otherwise: fiction does not mean false, and nonfiction does not mean true. For example, even though a fiction writer's characters and settings may be imaginary-as-in-not-real, the ideas, emotions, and dialogues lived through by those characters may correspond to reality. Contrariwise, even though a nonfiction writer's subject matter may correspond to reality, the distinctions, characterizations, and theories they develop may be imaginary-as-in-not-real.
The point being that even if we were to say that science is fiction, we would not necessarily be saying that it is false; only that it is a product of creativity and imagination that may or may not correspond to reality.
Now, is this latter the case with science? Yes and no. For within the scientific method both fiction and nonfiction appear. The scientist observes and then hypothesizes (fictionalizes) about the observation, performs experiments to test the fiction, and finally - based on the results of the experiments - comes to a conclusion regarding the truth or falsity of the fiction. If the fiction is not shown to be false by the experiments, it is then treated as nonfiction, otherwise it is cast into the scientific dustbin of imaginary-as-in-not-real hypotheses...