The invention discloses a bed limb exerciser which is characterized in that the exerciser comprises an upper limb moving mechanism, a lower limb moving mechanism, a transversal beam assembly and a bracket assembly, wherein the upper limb moving mechanism comprises a front rotary disc, a front rotary shaft, a front bearing, a front machine leg and a rotary handle; the lower limb moving mechanism comprises a rear rotary disc, a rear rotary shaft, a rear bearing, a rear machine leg and a pedal; the transversal beam assembly comprises a front transversal beam, a transversal beam sleeve barrel anda rear transversal beam; and the bracket assembly comprises a front bracket, a rear bracket, a front bracket base and a rear bracket base. When a patient uses the exerciser, the length, height, exercising amount and the like of the exerciser can be changed by adjusting the limiting hole according to the self condition, and the exercising intensity can be changed by a friction accentuator. The invention has no need of moving hemiplegics or paraplegics, and then enables the patient to do self movement treatment, thereby lightening the workload of nursing people and the pain of the patients due to long-term sitting exercise, and preventing the damage to the bodies caused by keeping sitting for a long term; the structure is simple; and the cost is low.