We successfully synthesized the new intermetallic compound Gd5Ni19 and determined its crystal structure by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The structure is a Sm5Co19-type superlattice structure (2H, space group P6(3)/mmc), and the lattice parameters were determined as a = 0.4950(1) nm and c = 3.2161(5) run by X-ray Rietveld refinement. The XRD results agreed with the STEM analysis results. The P-C isotherm of Gd5Ni19 was measured at 233 K. In the first absorption cycle, the maximum hydrogen capacity reached 1.07 H/M at 2.0 MPa. The sloping plateau was observed in the first absorption-desorption cycle. The maximum hydrogen capacity decreased by 0.87 H/M in the second absorption cycle, implying that hydrogen in the amount of H/M = 0.20 remained in the alloy before the second absorption - desorption cycle.