Which version of SQL Developer are you using and how exactly are you running your scripts?
Using the latest version (17.3.1.279), when I run scripts calling them with @, the spooled output goes to %APPDATA%\Sql Developer\
But if I open the SQL file then run it in script mode (F5) the results go wherever I opened the file:
C:\Users\csaxon\Documents\Scripts>dir output
Volume in drive C is System
Volume Serial Number is 4416-06A6
Directory of C:\Users\csaxon\Documents\Scripts\output
19/10/2017 15:09 <DIR> .
19/10/2017 15:09 <DIR> ..
0 File(s) 0 bytes
2 Dir(s) 97,226,600,448 bytes free
C:\Users\csaxon\Documents\Scripts>type spool-test.sql
spool output\out.log
select 'SPOOLED' t from dual;
spool off
-- open spool-test.sql in SQL Developer, hit F5 then
C:\Users\csaxon\Documents\Scripts>dir output
Volume in drive C is System
Volume Serial Number is 4416-06A6
Directory of C:\Users\csaxon\Documents\Scripts\output
19/10/2017 15:10 <DIR> .
19/10/2017 15:10 <DIR> ..
19/10/2017 15:10 28 out.log
1 File(s) 28 bytes
2 Dir(s) 97,226,989,568 bytes free
C:\Users\csaxon\Documents\Scripts>type output\out.log
T
SPOOLED
This is what you're looking for, right?
Or, if you're using SQLcl, you can use cd in this to change the directory, just like you would at the command prompt. So you can set the directory as needed:
C:\Users\csaxon\Documents\Scripts>type spool-test-cl.sql
cd output
spool clout.log
select 'SPOOLED' t from dual;
spool off
C:\Users\csaxon\Documents\Scripts>sql.exe chris/xxxxx@db
SQLcl: Release 17.3.0 Production on Thu Oct 19 15:07:08 2017
Copyright (c) 1982, 2017, Oracle. All rights reserved.
Last Successful login time: Thu Oct 19 2017 15:07:11 +01:00
Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
SQL> @spool-test-cl
T
SPOOLED
SQL> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
C:\Users\csaxon\Documents\Scripts>dir output
Volume in drive C is System
Volume Serial Number is 4416-06A6
Directory of C:\Users\csaxon\Documents\Scripts\output
19/10/2017 15:12 <DIR> .
19/10/2017 15:12 <DIR> ..
19/10/2017 15:12 28 clout.log
19/10/2017 15:10 28 out.log
2 File(s) 56 bytes
2 Dir(s) 97,223,872,512 bytes free
C:\Users\csaxon\Documents\Scripts>type output\clout.log
T
SPOOLED