Cover - USD ($)	12 Months Ended
	Mar. 31, 2021	Jul. 22, 2021	Sep. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2021
Current Fiscal Year End Date	--03-31
Entity File Number	033-17773-NY
Entity Registrant Name	ROCKETFUEL BLOCKCHAIN, INC.
Entity Central Index Key	0000823546
Entity Tax Identification Number	90-1188745
Entity Incorporation, State or Country Code	NV
Entity Address, Address Line One	201 Spear Street
Entity Address, Address Line Two	Suite 1100
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	424
Local Phone Number	256-8560
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 29,199,000
Entity Common Stock, Shares Outstanding		24,988,416