  The neutron diffraction and nuclear magnetic resonance (NMR) measurements
have been used to microscopically analyze the magnetic structure in the $S =
1/2$ kagome antiferromagnet CdCu$_{3}$(OH)$_{6}$(NO$_{3}$)$_{2}\cdot $H$_{2}$O.
Below the magnetic ordering temperature $T_N\simeq 4$ K, magnetic Bragg
reflections at (110) and (100) were found in the neutron diffraction pattern,
which suggests a $q=0$ magnetic structure. Furthermore, the vector spin
chirality for the $q=0$ structure was successfully identified from the internal
field direction obtained by the $^{14}$N-NMR measurement. Our findings point to
a chirality-ordered magnetic structure with negative vector chirality and
$\langle 100 \rangle$ anisotropy.
