working experience means experience that works
Working is used an adjective to describe a person doing some form of work or labor; such as: a working person. An working woman
It is also utilized to describe something working/functioning; as: an working model, an working knowledge of English.
It is not usually used to describe experience.
Work experience is the experience that a person has during working in a job, or working in a specific field or occupation, such as:
Four years of qualifying work experience in the field of Marketing.
Work experience can be projected in the right way such as: work experience in a responsible capacity or having associated with decision making process.