Citizen of Andorra, Argentina, Australia, Bolivia, Brazil, Brunei, Bulgaria, Canada, South Korea, Costa Rica, Chile, Cyprus, El Salvador, Guatemala, Holy See, Honduras, Iceland, Israel, Japan, Malaysia, Malta, Mexico, Monaco, Nicaragua, Norway, New Zealand, Panama, Paraguay, Republic of Croatia, Romania, San Marino, Seychelles, Singapore, Switzerland, Uruguay, Venezuela, Hong Kong (Sar), Macao (Ear) and citizens of the European Union do not need visa to enter Spain for tourism or business purposes. Except for the citizens of EFTA/EU, your stay can not exceed 90 days over a 180 days period.
Other nationals generally require visas, which must be obtained from Spanish consulates abroad. Current list of Spanish consulates abroad you may find here:
Immigration (in Romanian)