A fixing device includes a fixing rotary body and a pressing rotary body disposed opposite the fixing rotary body. A pivotable pressurization member contacts and presses the pressing rotary body against the fixing rotary body. A pressurization pivot is provided on the pressurization member. A depressurization member, pivotable about the pressurization pivot, causes the pressurization member to isolate the pressing rotary body from the fixing rotary body. A depressurization pivot is provided on the depressurization member. A lock is pivotable about the depressurization pivot and engageable with the pressurization pivot. A biasing member, anchored to the lock, exerts a resilient bias that allows the lock to cause the pressurization member to press the pressing rotary body against the fixing rotary body. A detent is situated in a pivotal trajectory of the lock to restrict pivot of the lock by contacting the lock.