Document And Entity Information - USD ($)	12 Months Ended
	Apr. 30, 2020	Jul. 10, 2020	Oct. 31, 2019
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	Non-accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding (in shares)		74,398,262
Entity Public Float			$ 28,506,324
Entity Shell Company	false
Document Type	10-K
Document Period End Date	Apr. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Title of 12(g) Security	Common Stock $.01 Par Value