Marine macroalgae are an attractive source for biorefineries as an alternative to terrestrial crops, and new, sustainable macroalgae biomass fractionation methods are needed. One of the least investigated macroalgae-derived products is starch. In this work, we report on a device and a protocol for pretreatment for starch extraction from a green macroalga Ulva ohnoi (U. ohnoi) with an emerging, nonthermal, and environmental friendly technologypulsed electric field (PEF). Using the custom-made insulated gate bipolar transistor-pulsed generator combined with a gravitation press-electrode device, we show that 200 pulses with a field strength of 1 kV cm −1 , pulse duration of 50 μs, and pulse repetition rate of 3 Hz concentrate the starch in the U. ohnoi biomass by 59.38% by removing the salts, proteins, and other small molecules. The starch extraction yield from the PEF-pretreated biomass is 59.54 ± 1.34%, compared to 52.31 ± 3.21% from untreated biomass. In addition, PEF combined with pressing increased the coextracted macroalgae protein by more than 4 times and ash by 1.5 times in comparison with pressing alone. These results indicate the potential of PEF pretreatment for challenging macroalgae biomass fractionation in the sustainable marine biorefinery.