  The magnetic field effect on the phase diagram of the organic Mott system
$\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br in which the bandwidth was tuned by
the substitution of deuterated molecules was studied by means of the
resistivity measurements performed in magnetic fields. The lower critical point
of the first-order Mott transition, which ended on the upper critical field
$H_{\rm c2}$-temperature plane of the superconductivity, was determined
experimentally in addition to the previously observed upper critical end point.
The lower critical end point moved to a lower temperature with the suppression
of $T_{\rm c}$ in magnetic fields and the Mott transition recognized so far as
the $S$-shaped curve reached $T =$ 0 when $H > H_{\rm c2}$ in the end.
