Document and Entity Information	12 Months Ended
	Dec. 31, 2017 shares
Document and Entity Information [Abstract]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Entity Registrant Name	OPTIBASE LTD
Entity Central Index Key	0001077618
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding	5,214,256