A wheelchair is disclosed having two adjustment structures for allowing adjustment of the elevation of two handlebars relative to the two parallel vertical main frame bars thereof, each adjustment structure including a holder block fixedly provided at the top of the respective vertical main frame bar to accommodate the respective handlebar, a holding down block movably mounted in the holder block, and a locking lever pivoted to the holder block for moving a locating rod into one of a vertically aligned series of locating holes at the respective handlebar and forcing the holding down block against the respective handlebar.