The control method of a sheet manufacturing apparatus and a sheet manufacturing apparatus

When starting a sheet manufacturing device from a stopped state， trouble that can occur during start is avoided and the sheet manufacturing device is transitioned to a stable operation state. This sheet manufacturing device is provided with a deposition unit (60) which rotates a drum unit (61) in which multiple openings are formed and which discharges fibers; a second web forming unit (70) which operates a mesh belt (72) to form a second web (W2)， a sheet forming unit (80) which forms a sheet (S) from the second web (W2)， and a control unit which performs start control for moving the deposition unit (60) and the second web forming unit (70) from the stopped state， wherein， when performing start control from a state in which fibers are present in the drum unit (61)， the control unit adjusts the thickness of the second web (W2) by controlling at least one of the timing for starting rotation of the drum unit (61)， the rotation speed of the drum unit (61)， the timing for starting movement of the mesh belt (72) and the movement speed of the mesh belt (72). When starting a sheet manufacturing device from a stopped state， trouble that can occur during start is avoided and the sheet manufacturing device is transitioned to a stable operation state. This sheet manufacturing device is provided with a deposition unit (60) which rotates a drum unit (61) in which multiple openings are formed and which discharges fibers; a second web forming unit (70) which operates a mesh belt (72) to form a second web (W2)， a sheet forming unit (80) which forms a sheet (S) from the second web (W2)， and a control unit which performs start control for moving the deposition unit (60) and the second web forming unit (70) from the stopped state， wherein， when performing start control from a state in which fibers are present in the drum unit (61)， the control unit adjusts the thickness of the second web (W2) by controlling at least one of the timing for starting rotation of the drum unit (61)， the rotation speed of the drum unit (61)， the timing for starting movement of the mesh belt (72) and the movement speed of the mesh belt (72).