The determination of the energy source for emission lines in LINERs
 is one of the most important issues related with active galactic
 nuclei. Is it a power-law continuum source or a shock? The
 determination of the energy source is a crucial test whether or not
 there exist massive black holes in their nuclei. However, we have
 not reached a conclusion yet, because of the limitations of optical
 diagnostic line measurements and direct UV spectroscopic searches
 for power-law continuum. We propose infrared spectroscopy of LINERs
 which show broad Balmer line components. Although those broad lines
 are weak, their existence suggests that this class of LINERs might
 have massive black holes in their nuclei. We will determine the
 ionization/excitation mechanisms for emission lines for these
 LINERs, using infrared diagnostic lines, most of which are not
 observable by ground-based telescopes or are very difficult to
 measure. Because LINERs with broad Balmer lines are rather common,
 this is also a critical test of the frequency of massive black
 holes in galactic nuclei.