The weak value, proposed by Aharonov et al. in 1988, has been
applied for various fields of physics for the purpose of precision
measurement, which is made possible with the help of the 'postselection'
specifying actively the final state in the physical process. Here we
have considered the feasibility of applying the weak measurement in high
energy particle physics, especially in measuring the CP-violating
parameters in B meson decays, where the effective lifetime of the decay
mode is expected to be prolonged statistically due to the postselection.
Our analysis shows that, when adopted in the Belle II experiment at the
SuperKEKB collider, the effective lifetime may be prolonged up to 2.6
times, and that the measurement precision of the CP-violating parameters
may be improved by about 20%.