  We report the in-plane penetration depth $\lambda_{\parallel}$ of single
crystals $\kappa$-(BEDT-TTF)$_2X$ ($X=$ Cu(NCS)$_2$ and Cu[N(CN)$_2$]Br) by
means of the reversible magnetization measurements under the control of
cooling-rate. In $X$ = Cu(NCS)$_2$, $\lambda_{\parallel}(0)$ as an
extrapolation toward $T$ = 0 K does not change by the cooling-rate within the
experimental accuracy, while $T_{\textrm{c}}$ is slightly reduced. On the other
hand, in $X$ = Cu[N(CN)$_2$]Br, $\lambda_{\parallel}(0)$ indicates a distinct
increase by cooling faster. The different behavior of $\lambda_{\parallel}(0)$
on cooling-rate between the two salts is quantitatively explained in terms of
the local-clean approximation (London model), considering that the former salt
belongs to the very clean system and the later the moderate clean one. The good
agreement with this model demonstrates that disorders of ethylene-group in
BEDT-TTF introduced by cooling faster increase the
electron(quasiparticle)-scattering, resulting in shorter mean free path.
