Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Document Information [Line Items]
Entity Central Index Key	0001046203
Entity Registrant Name	Guaranty Federal Bancshares Inc
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2020
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	0-23325
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	43-1792717
Entity Address, Address Line One	2144 E Republic Rd, Suite F200
Entity Address, City or Town	Springfield
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	65804
City Area Code	833
Local Phone Number	875-2492
Title of 12(b) Security	Common Stock, Par Value $0.10 per share
Trading Symbol	GFED
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		4,367,510