Document And Entity Information - USD ($)	12 Months Ended
	Oct. 01, 2016	Oct. 27, 2016	Apr. 02, 2016
Document Information [Line Items]
Entity Registrant Name	INSTEEL INDUSTRIES INC
Entity Central Index Key	0000764401
Trading Symbol	iiin
Current Fiscal Year End Date	--10-01
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		18,975,641
Entity Public Float			$ 507,817,830
Document Type	10-K
Document Period End Date	Oct. 01, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Amendment Flag	false