A semiconductor integrated circuit according to the present invention comprises a clock tree circuit for delay-adjusting a clock signal using various delay amounts, and a clock synchronizing circuit to which the delay-adjusted clock signal is supplied. The clock tree circuit comprises a first clock tree cell provided in a poststage of a clock signal introducing terminal, a second clock tree cell provided in a prestage of the clock synchronizing circuit and a poststage of the first clock tree cell, and a clock ramification point provided in a prestage of the second clock tree cell. The clock synchronizing circuit comprises a first clock synchronizing circuit to which the clock signal delay-adjusted by the second clock tree cell and thereafter outputted from the clock tree circuit is supplied, and a second clock synchronizing circuit to which the clock signal outputted from the clock tree circuit at the clock ramification point is supplied.