  The Kuramoto-Daido model, which describes synchronization phenomena, is a
system of ordinary differential equations on $N$-torus defined as coupled
harmonic oscillators, whose natural frequencies are drawn from some
distribution function. In this paper, the continuous model for the
Kuramoto-Daido model is introduced and the linear stability of its trivial
solution (incoherent solution) is investigated. Kuramoto's transition point
$K_c$, at which the incoherent solution changes the stability, is derived for
an arbitrary distribution function for natural frequencies. It is proved that
if the coupling strength $K$ is smaller than $K_c$, the incoherent solution is
asymptotically stable, while if $K$ is larger than $K_c$, it is unstable.
