Document And Entity Information - shares	9 Months Ended
	Jan. 31, 2019	Mar. 15, 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 Emerging Growth Company	false
Entity Small Business	true
Entity Common Stock, Shares Outstanding (in shares)		64,050,508
Document Type	10-Q
Document Period End Date	Jan. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false