Laser-induced fluorescence spectroscopy using a single-longitudinal-mode diode laser has been applied to investigating isotope shifts and the hyperfine structures of gadolinium in the wavelength region of 400nm. Six absorption spectra of transitions from the ground and low-lying metastable levels were measured. The isotope shift per unit mass change varied from 0.6 to 1.0GHz depending on the transition. The hyperfine splitting constants of (157)Gd and (155)Gd isotopes were determined for the six upper levels of the transitions. The absorption spectrum of the 999-25661 cm(-1) transition showed the narrowest spectral width for odd isotopes.