To provide an ink which generates no forward flow phenomenon in a high-temperature high-humidity environment and therefore provides an excellent writing touch without causing any unclear trace of writing, and a ball-point pen using this.

The ink for ball-point pens comprises a colorant, a resin, a solvent and globular fine particles of hydrophobic silica which satisfy the following conditions (i) and (ii) and have an average particle size of the primary particles of 0.01 to 5 μm: (i) when an organic compound which is in a liquid state at a room temperature and has a dielectric constant of 1 to 40 F/m is mixed and shaken with the silica fine particles in a weight ratio of 5:1, the silica fine particles are uniformly dispersed within the organic compound; (ii) when methanol is distilled off by an evaporator under a heated condition from a dispersion wherein the silica fine particles are dispersed in methanol, and subsequently the dispersion is maintained at 100°C for 2 hr, the amount of the remaining primary particles is ≥20% of the initial amount of the primary particles.