  We estimated the luminosity function (LF) of IRAS galaxies in the PSCz
catalogue. The faint end of the PSCz LF is slightly steeper than that of the LF
derived by Saunders et al. (1990; S90). Using an analytical form for the LF
used by S90, we obtain the following parameters: \alpha = 1.23 \pm 0.04,
L_*=(8.85 \pm 1.75) \times 10^8 h^{-2} L_\odot, \sigma =0.724 \pm 0.010, and
\phi_* = (2.34 \pm 0.30) \times 10^{-2} h^3 Mpc^{-3}. We also examined the
evolution in the sample by a simple assumption \phi_*(z) \propto (1+z)^P, and
found P=3.40 \pm 0.70. It does not affect the three parameters, \alpha, L_*,
and \sigma, but \phi_*(z=0) is overestimated up to \sim 15% if we ignore
evolution. We estimated the temperature dependence of the LF. The LFs of warm
and cool galaxies are quite different: the LF of warm galaxies has a very steep
faint end with \alpha =1.37. We also discuss a lump found at the brightest end
of the LF.
