We demonstrate a zero-crossing Shapiro step generated in a magnetically-coupled Josephson gate, where a long Josephson junction and a control line are placed in-line. The operation is based on the imbalanced evolution of the junction phases owing to the different amplitudes of the positive and negative critical current. A test circuit was fabricated using a Nb/AlO x /Nb junction technology. When we applied a rf signal of 15.2 GHz, we observed a Shapiro step that crossed the zero-current axis at

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... the voltage position of the 1st order. The experimental results were quantitatively reproduced by simulation.