The invention discloses a machining device of a gel pen capable of adjusting writing stability. The machining device comprises a machining table, vertical plates on the two sides of the machining table, and a first mounting plate arranged above the machining table; multiple machining grooves are formed in the machining table, limiting grooves are formed in the inner walls of the machining grooves,a first air cylinder is arranged on the first mounting plate, a piston rod of the first air cylinder is fixedly connected to the first mounting plate, a first conveying assembly is arranged on each vertical plate, a first push rod is arranged on the bottom of the first mounting plate, a first opening is formed in the first push rod, a fixed rod is arranged in each machining groove, a first movable cavity is formed in the inner wall of each limiting groove, a limiting block is arranged in each first movable cavity, and a second air cylinder used for driving the limiting blocks to move along the inner walls of the first movable cavities is arranged on the bottom of the machining table.