An externally pressurized air bearing spindle comprises: a first cylindrical bearing portion having a journal bearing surface opposing an outer circumferential surface of a main shaft with a small journal bearing clearance therebetween, a thrust bearing surface opposing one end surface of a thrust plate disposed on the main shaft with a small thrust bearing clearance therebetween, and plural bearing nozzles formed in the journal bearing surface and the thrust bearing surface and arranged in planes perpendicular to an axis thereof; and a second cylindrical bearing portion having a thrust bearing surface opposing the other end surface of the thrust plate with a small thrust bearing clearance therebetween and plural bearing nozzles formed in the thrust bearing surface and arranged in a plane perpendicular to an axis thereof; the arrangement being such that the main shaft is supported on the bearing surfaces without contact by the action of compressed air fed through the bearing nozzles into the bearing clearances, and that an annular groove is formed between an outer wall of at least one of the first and second bearing portions and an inner wall of an outer case for that one bearing portion so that the bearing nozzles are fed with compressed air from a bearing air feed port formed in the outer case through the annular groove.