The results of the development of the Marx generator intended to supply an electron accelerator with the electron beam extraction into gas through a foil window are presented. The generator has air insulation and consists of 4-6 stages, assembled in the form of artificial long lines with the wave impedance of ~4 Ω. To eliminate reflections, each of the lines is provided with a matched load. Connection of both the stages in series and matched loads to the stages is made by one block of switches. The generator provides obtaining rectangular voltage pulses of up to 130 -140 kV with the duration of 10 μs at the matched load and 5 μs at an arbitrary constant resistive load, respectively. Assembling the stages from two half-length parallel lines, results in possibility to increase the output voltage and current of the generator.