  We report on two superoutbursts of the AM CVn-type object CR Boo in 2014
April--March and 2015 May--June. A precursor outburst acompanied both of these
superoutbursts. During the rising branch of the main superoutburst in 2014, we
detected growing superhumps (stage A superhumps) whose period was
$0.017669(24)$ d. Assuming that this period reflects the dynamical precession
rate at the radius of the 3:1 resonance, we could estimate the mass ratio
($q=M_2/M_1$) of 0.101(4) by using the stage A superhump period and the orbital
one of 0.0170290(6) d. This mass ratio is consistent with that expected by the
theoretical evolutionary model of AM CVn-type objects. The detection of
precursor outbursts and stage A superhumps is the second case in AM CVn-type
objects. There are two interpretations of the outbursts of AM CVn-type objects.
One is a dwarf nova (DN) outbursts analogy, which is caused by thermal and
tidal instabilities. Another is the VY Scl-type variation, which is caused by
the variation of the mass-transfer rate of the secondary. This detection of the
superhump variations strongly suggests the former interpretation.
