Abstract: A tightening device with easy alignment is adapted for securing a ceiling fan to a fitting which is used to mount the ceiling fan onto a flat ceiling wall, and includes an annular flange member extending inwardly and radially from a lower annular wall of a protective covering member in the form of a canopy, and an anchored flat sheet formed with an upper major wall of a motor casing. The anchored flat sheet has an inner peripheral wall, and a plurality of first fastening positions proximate to the inner peripheral wall and angularly spaced apart from one another. An upper annular clamping member has an outer circumferential portion, and an inner circumferential portion extending inwardly and radially from the outer circumferential portion. When the clamping member is placed on the annular flange member, the outer circumferential portion will sandwich the annular flange member to the anchored flat sheet.