A purchasing agent is an employee within a company, business or other organization who is responsible at some level for buying or approving the acquisition of goods and services needed by the company. The purchasing agent’s responsibilities may be the same as that of a buyer or may include wider supervisory or managerial responsibilities. A Purchasing Manager may oversee the acquisition of materials needed for production, general supplies for offices and facilities, equipment, or construction contracts. A Purchasing Manager often supervises purchasing agents and buyers, but in small businesses the Purchasing Manager may also be the purchasing agent or buyer.
Source: wikipedia.org