A generator for an absorption refrigerator has heat transfer pipes within a shell main body, an absorbing solution injecting port and absorbing solution exhausting port. An absorbing solution exhausting port is provided which receives the absorbing solution flowing over a dam which is higher than the exhaust port on the absorbing solution injecting port side. A steam box is provided to cooperate with the absorbing solution exhausting port, which box has an opening above the top of the dam. The absorbing solution flowing in the main body injected from the injecting port (3) forms a closed type heat exchanger connected with an open type heat exchanger provided at the steam box into which the absorbing solution vaporizes as it flows over the dam (41) into the exhaust box (42).