A nonaqueous ink, having: colorant particles, the colorant particles having an average particle diameter of 1 nm or more and less than 50 nm, and the value (D90-D10) of being 100 nm or less, a dispersant; and a radical-polymerization compound; wherein D90-D10 is a value obtained by subtracting D10 from D90; D90 and D10 represent respectively the particle diameters at cumulative colorant particle numbers of 0.9 (90 number %) and 0.1 (10 number %) in an integral value of the distribution function dG=F(D)dD; and G represents the number of the pigment particles; and D represents the diameter of the particles.