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The spin-lattice relaxation rate 1/ T 1 and the Knight shift were measured for La 1.85 Sr 0.15 CuO 4 and YBa 2 Cu 4 O 8 under pressure to 1.4 GPa. The results together with the previously reported pressure dependence of the nuclear quadrupole frequency, ν Q , give evidence that the local hole distribution changes under pressure. In La 1.85 Sr 0.15 CuO 4 , the hole density in the Cu 3d orbit decreases, accompanying a suppression of the antiferromagnetic spin fluctuation of the low-energy component. In YBa 2 Cu 4 O 8 , by contrast, the spin fluctuation changes little while the total hole number in the CuO 2 plane increases. We argue that such changes in the hole distribution are responsible for the T c increase in the respective compounds. We also found that the so-called “spin-gap” behavior in YBa 2 Cu 4 O 8 becomes more pronounced under pressure.