This paper presents sensorless cooperation between human and mobile manipulator. In the past, research on cooperation between human and mobile manipulator used force sensor to sense human force. This research aims to develop sensorless cooperation by reaction torque observer instead of force sensor. Utilization of disturbance torque estimation on manipulator and task limitation due to mounted force sensor are considered in this research. Kinematics and dynamical model of mobile manipulator are estimated with Newton-Euler method. Robust acceleration control is established with disturbance observer, Reaction torque is estimated from disturbance torque and dynamical model. Cooperative control method based on human force estimation is proposed using impedance control on virtual workspace. Finally, the model and the proposed methods are confirmed through experiment.