I completely agree with AronWarwick. It is a technically and grammatically correct sentence, but one you wouldn't ever use, since you would only have an office "at my job" or "at work." Americans only use "the job" when the job site changes frequently, but the person you are speaking with knows exactly which job you are referring to, as in "I have a big office at the job (this week)" with the words in parenthesis being implied and understood, but not stated.
It is a technically correct sentence but it wouldn't be used anywhere to my knowledge. It's important to remember when an exactly literal translation doesn't make much sense. The only time I could see it being remotely plausible would be to an accountant or similar who is temporarily working for a company and that company has provided him with a big office for that time.