In this study, a pneumatically contracting active cloth has been developed; its application is proposed for a safe sitting-posture recovery system for wheelchair users to avoid fall-related accidents. The active cloth consists of thin artificial muscles knitted via a flat string machine. The safe wheelchair system is configured with an active cloth and seating pressure sensor. The seating pressure sensor, located on the seating surface of the wheelchair, estimates the inclination of the upper body of the user; when this reaches an angle that is dangerous for falling from the wheelchair, the active cloth contracts to correct the posture of the upper body. In this paper, we clarify the fabrication process and fundamental characteristics of the active cloth and indicate its potential as a mechanical element for welfare apparatuses by demonstrating a safe wheelchair system.