That depends if he is in your supervisory chain. Here is what AR 623-3 states about the establishing the rating chain:
AR 623-3 Extract:
CDRs, commandants, and organization leaders will establish rating chains and publish rating schemes within their units or organizations in accordance with locally developed procedures and ARs. Established rating chains will correspond as nearly as practicable to the chain of command or supervision within a unit or organization, regardless of component or geographical location. Rating schemes will identify the name of the rated Soldier and the effective date for each of the rating officials (date on which the rating official assumed his or her role as the rating official for the rated Soldier). Rating schemes will be published and made accessible, either manually or electronically, to each rated Soldier and each member of the rating chain. Any changes to a rating scheme will be published and distributed, as required. No changes may be retroactive.
The rater should be the individual that supervises your day to day activities.