A gas discharge excitation laser device having an improved response of an actual output to transition from a laser output ON command to a laser output OFF command. When a command output is switched from ON to OFF at time it2 after passing an ON period Ton, an output command voltage Voc is once suddenly reduced to an OFF-period bottom value Vbott lower than a value VB1 which is suitable for maintaining a base discharge current when laser gas is cold, and then is increased to the value VB1 in a period .tau.. Thus, the actual output is permitted to be instantly interrupted without stopping the discharge. Vbott is a function of .eta.=(Pc/Pmax).times.Beam ON period, and is gradually reduced to a lower-limit clamp value VB2. Vbott(.eta.)=VB1-[(VB1-VB2)/.eta.B2].eta. (where 0.ltoreq..eta..ltoreq..eta.B), Vbott(.eta.)=VB2 (where .eta.>.eta.B). In the equations, Pc is a laser output during the beam ON period, Pmax is a maximum rated laser output, and .eta.B2 is a value of .eta. when Vbott(.eta.) is reduced to VB2.