A numerical controller suppresses change of a axis speed to be slow even when a lookahead distance varies with small steps. The numerical controller includes: a lookahead unit that looks ahead a plurality of instruction blocks from an NC program; an analysis unit that analyzes the looked ahead instruction blocks and creates motion instruction data; a target speed calculation unit that calculates a target speed of the axis based on a lookahead distance; an interpolation unit that generates interpolation data based on the motion instruction data and the target speed; and a servo control unit that controls a motor based on the interpolation data. The target speed calculation unit refrains from recalculation of the target speed when a change of the lookahead distance is within a margin.