A highchair has a seat device, a bracket device and a table. The seat device has a base, a supporting sleeve and a seat. The bracket device is connected to the seat device and has two connecting segments, a connecting frame and a supporting arm. The connecting segments are respectively connected securely to the supporting sleeve and each has a connecting mount, a button seat, a pressing button and a button spring. The connecting frame connects to the connecting segments and has two inserting segments and a primary frame. The supporting arm is telescopically and pivotally connected to the connecting frame. The table is detachably mounted on the bracket device.