Document And Entity Information - shares	9 Months Ended
	Jun. 30, 2020	Jul. 15, 2020
Document Information [Line Items]
Entity Central Index Key	0000796505
Entity Registrant Name	Clearfield, Inc.
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	Q3
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	0-16106
Entity Incorporation, State or Country Code	MN
Entity Tax Identification Number	41-1347235
Entity Address, Address Line One	7050 Winnetka Avenue North, Suite 100
Entity Address, City or Town	Brooklyn Park
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55428
City Area Code	763
Local Phone Number	476-6866
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	CLFD
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		13,647,005