A three-dimensional object printing apparatus includes a liquid discharge head having a nozzle surface provided with a nozzle array including a plurality of nozzles for discharging a liquid, a moving mechanism that changes a position of the liquid discharge head with respect to a three-dimensional workpiece, and a sensor that detects a positional relationship of the liquid discharge head with respect to the workpiece, in which when an axis parallel to a normal line of the nozzle surface is set as a first axis, an axis parallel to the nozzle surface and intersecting an extending direction of the nozzle array is set as a second axis, and an axis that intersects both the first axis and the second axis is set as a third axis, the sensor detects a relative positional relationship of the liquid discharge head with respect to the workpiece in a direction along the third axis.