We analyzed spectral data of the astrophysical diuse emission obtained with the low-resolution spec- troscopy mode on the AKARI InfraRed Camera (IRC) in the 1.8-5.3 μm wavelength region. Advanced reduction methods specialized for slit spectroscopy of diuse sky spectra have been developed, and a catalog of 278 spectra of the diffuse sky covering a wide range of Galactic and ecliptic latitudes was constructed. Using this catalog, two other major foreground components, the zodiacal light (ZL) and the diuse Galactic light (DGL), were separated and subtracted by taking correlations with ZL brightness es- timated by the DIRBE ZL model and with the 100 μm dust thermal emission, respectively. The isotropic emission was interpreted as the extragalactic background light (EBL), which shows significant excess over the integrated light of galaxies at <4 μm.