Document and Entity Information - shares	9 Months Ended
	Jul. 31, 2020	Sep. 09, 2020
Document and Entity Information [Abstract]
Entity Central Index Key	0000036840
Current Fiscal Year End Date	--10-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jul. 31, 2020
Entity File Number	000-25043
Entity Registrant Name	FIRST REAL ESTATE INVESTMENT TRUST OF NEW JERSEY
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	22-1697095
Entity Address, Address Line One	505 Main Street
Entity Address, City or Town	Hackensack
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	07601
City Area Code	201
Local Phone Number	488-6400
Title of 12(b) Security	Shares of beneficial interest, without par value
Trading Symbol	FREVS
Name of Exchange on which Security is Registered	NONE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		6,856,651