Document And Entity Information - USD ($)	12 Months Ended
	Apr. 30, 2017	Jul. 14, 2017	Oct. 31, 2016
Document Information [Line Items]
Entity Registrant Name	BUTLER NATIONAL CORP
Entity Central Index Key	0000015847
Trading Symbol	buks
Current Fiscal Year End Date	--04-30
Entity Filer Category	Smaller Reporting Company
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		64,543,550
Entity Public Float			$ 9,377,954
Document Type	10-K
Document Period End Date	Apr. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false